include ../_util-fns

:marked
  Welcome to the Angular 2 Style Guide
  
  欢迎光临Angular 2风格指南

  ## Purpose
  ## 目的

  If you are looking for an opinionated style guide for syntax, conventions, and structuring Angular applications, then step right in.
  
  如果你在为语法，规则和Angular应用程序结构寻找一个特定的风格指南，请继续阅读。

  The purpose of this style guide is to provide guidance on building Angular applications by showing the conventions we use and, more importantly, why we choose them.
  
  本风格指南的目的是，通过展示我们使用的规则，更加重要的，展示我们为什么要选择它们，来为建造Angular应用程序提供一个向导。
.l-main-section

:marked
  ## Style Vocabulary
  ## 风格词汇

  Each guideline describes either a good or bad practice, and all have a consistent presentation.
  
  每一个向导描述一个好的或者坏的实践，所有的向导都有一个统一的展示。

  The wording of each guideline indicates how strong the recommendation is.
  
  每个向导使用词汇来标志我们推荐的强度。

.s-rule.do
  :marked
    **Do** is one that should always be followed.   
    _Always_ might be a bit too strong of a word.    
    Guidelines that literally should always be followed are extremely rare.
    On the other hand, we need a really unusual case for breaking a *Do* guideline.
    **做**是我们一直要遵循的规则。
    _一直_该词可能有点太强。
    指南中标明应该一直遵循的非常少见。但另一方面，我们需要一个非常不常见的情况来打破一个*做*的指南。

.s-rule.consider
  :marked
    **Consider** guidelines should generally be followed.
    **考虑**指南是通常应该遵循的。    
    If you fully understand the meaning behind the guideline and have a good reason to deviate, then do so. Please strive to be consistent.
    如果你能完全理解指南背后的意思，并且有一个很好的理由越轨，那就这么办。但是请保持一致性。

.s-rule.avoid
  :marked
    **Avoid** indicates something we should almost never do. Code examples to *avoid* have an unmistakeable red header.
    **避免**表示我们永远不应该这么做某事。需要*避免*的代码例子会有一个不会错过红色标题。
.l-main-section

:marked
  ## File Structure Conventions
  ## 文件结构规则

  Some code examples display a file that has one or more similarly named companion files. (e.g. hero.component.ts and hero.component.html).
  
  一些代码例子中会有一个文件，拥有一个或多个相似名字的伴随文件。（比如，hero.component.ts和hero.component.html)。

  The guideline will use the shortcut `hero.component.ts|html|css|spec` to represent those various files. Using this shortcut makes this guide's file structures easier to read and more terse.
  
  该指南将会使用`hero.component.ts|html|css|spec`的简写来表示上面的多个文件。使用这个简写可以让本指南文件结构更容易被阅读，更加简洁。

.l-main-section
a(id='toc')

:marked
  ## Table of Contents
  ## 目录

    1. [Single Responsibility](#single-responsibility)    
    1. [单一职责](#single-responsibility)    
    1. [Naming](#naming)
    1. [命名规则](#naming)    
    1. [Coding Conventions](#coding-conventions)
    1. [代码规则](#coding-conventions)    
    1. [Application Structure](#application-structure)
    1. [应用程序结构](#application-structure)    
    1. [Components](#components)
    1. [组件](#components)    
    1. [Directives](#directives)
    1. [指令](#directives)    
    1. [Services](#services)
    1. [服务](#services)    
    1. [Data Services](#data-services)
    1. [数据服务](#data-services)    
    1. [Lifecycle Hooks](#lifecycle-hooks)
    1. [生命周期钩子](#lifecycle-hooks)    
    1. [Routing](#routing)
    1. [路由](#routing)    
    1. [Appendix](#appendix)
    1. [附录](#appendix)    

.l-main-section
:marked
  ## Single Responsibility
  ## 单一职责

  We apply the [Single Responsibility Principle](https:\/\/en.wikipedia.org/wiki/Single_responsibility_principle) to all Components, Services, and other symbols we create. 
  This helps make our app cleaner, easier to read and maintain, and more testable.
  
  我们对我们创建的所有组件、服务和其它标志等，应用[单一职责原则](https:\/\/en.wikipedia.org/wiki/Single_responsibility_principle)。这样能帮助把我们的应用程序弄的干净、易读、易于维护和易测试。

  ### Rule of One
  ### 单一规则
  <a id="01-01"></a>
  #### Style 01-01
  #### 风格 01-01
.s-rule.do
  :marked
    **Do** define one thing (e.g. service or component) per file.
    
    **做** 每个文件定义一个东西（比如服务或者组件）。

.s-rule.consider
  :marked
    **Consider** limiting files to 400 lines of code.
    
    **考虑** 限制文件到400行代码之内。

.s-why
  :marked
    **Why?** One component per file makes it far easier to read, maintain, and avoid collisions with teams in source control.
    
    **为什么？** 一个组件一个文件，让它非常容易阅读、维护，并且能防止在版本控制里与团队冲突。

.s-why
  :marked
    **Why?** One component per file avoids hidden bugs that often arise when combining components in a file where they may share variables, create unwanted closures, 
    or unwanted coupling with dependencies.
    
    **为什么？** 一个组件一个文件可以防止一些隐蔽错误，这些错误在经常在合并一些共享变量的组件到一个文件时发生，创建不希望的闭合或者依赖耦合。

.s-why.s-why-last
  :marked
    **Why?** A single component can be the default export for its file which facilitates lazy loading with the Component Router.
    
    **为什么？** 一个单独的组件能是该文件默认的输出，可以支持组件路由的懒加载。
:marked
  The key is to make the code more reusable, easier to read, and less mistake prone.
  
  关键是让代码可以重用，更易阅读和少一些易出的错误。

  The following *negative* example defines the `AppComponent`, bootstraps the app, defines the `Hero` model object, and loads heroes from the server ... all in the same file. *Don't do this*.
  
  下面的*负面*例子定义了一个`AppComponent`，该组件引导了应用程序，定义了`Hero`模型对象，并且从服务器加载了英雄 ... 所有都在同一个文件。 *不要这么做*。

+makeExample('style-guide/ts/01-01/app/heroes/hero.component.avoid.ts', '', 'app/heroes/hero.component.ts')(avoid=1)
:marked
  Better to redistribute the component and supporting activities into their own dedicated files.
  
  将组件和支持行为重新分配到它们自己独立的文件会更好。

+makeTabs(
  `style-guide/ts/01-01/app/main.ts,
  style-guide/ts/01-01/app/app.component.ts,
  style-guide/ts/01-01/app/heroes/heroes.component.ts,
  style-guide/ts/01-01/app/heroes/shared/hero.service.ts,
  style-guide/ts/01-01/app/heroes/shared/hero.model.ts,
  style-guide/ts/01-01/app/heroes/shared/mock-heroes.ts`,
  '',
  `app/main.ts,
  app/app.component.ts,
  app/heroes/heroes.component.ts,
  app/heroes/shared/hero.service.ts,
  app/heroes/shared/hero.model.ts,
  app/heroes/shared/mock-heroes.ts`)

:marked
  As the app grows, this rule becomes even more important.
  
  随着应用程序的长大，本规则会变得更加重要。

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.l-main-section
:marked
  ### Small Functions
  ### 小函数
  <a id="01-02"></a>
  #### Style 01-02
  ### 风格01-02
.s-rule.do
  :marked
    **Do** define small functions
    **做** 定义小的函数

.s-rule.consider
  :marked
    **Consider** limiting to no more than 75 lines.
    **考虑** 限制在75行之内
.s-why
  :marked
    **Why?** Small functions are easier to test, especially when they do one thing and serve one purpose.
    
    **为什么？** 小函数更加容易被测试，特别是当它们只做一件事，为一个目的服务的时候。

.s-why
  :marked
    **Why?** Small functions promote reuse.
    
    **为什么？** 小函数促进代码重用。

.s-why
  :marked
    **Why?** Small functions are easier to read.
    
    **为什么？** 小函数更加容易阅读。

.s-why
  :marked
    **Why?** Small functions are easier to maintain.
    
    **为什么？** 小函数更加容易维护。

.s-why.s-why-last
  :marked
    **Why?** Small functions help avoid hidden bugs that come with large functions that share variables with external scope, create unwanted closures, or unwanted coupling with dependencies.
    
    **为什么？** 小函数帮助避免一些大函数与外界互相共享变量、创建不想要的闭合和依赖耦合时带来的一些隐蔽的错误。

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.l-main-section
:marked
  ## Naming
  ## 命名规则

  Naming conventions are hugely important to maintainability and readability. This guide recommends naming conventions for the file name and the symbol name.
  
  命名规则是一个对维护性和可读性非常重要。本指南为文件名和标志名字推荐了命名规则。 

.l-main-section
:marked
  ### General Naming Guidelines
  ### 常规命名指南
  <a id="02-01"></a>
  #### Style 02-01
  #### 风格02-01

.s-rule.do
  :marked
    **Do** use consistent names for all symbols.
    
    **做** 为所有标志使用一致的名字。
    
.s-rule.do
  :marked
    **Do** follow a pattern that describes the symbol's feature then its type. The recommended pattern is `feature.type.ts`.
    
    **做** 遵循一个模式来描述一个标志的特性和它的类型。推荐的模式为`feature.type.ts`。

.s-why
  :marked
    **Why?** Naming conventions help provide a consistent way to find content at a glance. Consistency within the project is vital. Consistency with a team is important. 
    Consistency across a company provides tremendous efficiency.
    
    **为什么？** 命名规则帮助我们提供了一个持续的方法来快速找到内容。在整个项目内前后一致至关重要。在团队内前后一致也很重要。在公司内部保持一致性可以大幅提高效率。

.s-why
  :marked
    **Why?** The naming conventions should simply help us find our code faster and make it easier to understand.
    
    **为什么？** 命名规则应该简单地帮助我们快速找到我们的代码并让它更加容易被理解。

.s-why.s-why-last
  :marked
    **Why?** Names of folders and files should clearly convey their intent. For example, `app/heroes/hero-list.component.ts` may contain a component that manages a list of heroes.
    
    **为什么？** 目录的名字和文件应该清楚的说明它们的用途。比如`app/heroes/hero-list.component.ts`包含了一个用来维护英雄列表的组件。

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.l-main-section
:marked
  ### Separate File Names with Dots and Dashes
  ### 使用点和横杠来分离文件名字
  <a id="02-02"></a>
  #### Style 02-02
  #### 风格02-02

.s-rule.do
  :marked
    **Do** use dashes to separate words.
    
    **做** 使用横杠来分离单词。

.s-rule.do
  :marked
    **Do** use dots to separate the descriptive name from the type.
    
    **做** 使用点来分离描述性名字和类型名字。

.s-rule.do
  :marked
    **Do** use consistent names for all components following a pattern that describes the component's feature then its type. A recommended pattern is `feature.type.ts`.
    
    **做** 对所有组件使用一致的命名规则，遵循这个模式：描述组件的特征，然后它的类型。一个推荐的模式为`feature.type.ts`。

.s-rule.do
  :marked
    **Do** use conventional suffixes for the types including `*.service.ts`, `*.component.ts`, `*.pipe.ts`. Invent other suffixes where desired, but take care in having too many.
    
    **做** 使用依照惯例的后缀来描述类型，包括`*.service.ts`、`*.component.ts`、`*.pipe.ts`。如果你想，你可以发明其它的后缀，但是请注意不要有太多。

.s-why
  :marked
    **Why?** Provides a consistent way to quickly identify what is in the file.
    
    **为什么？** 体统一个统一的方法来快速的确认一个文件是什么。

.s-why
  :marked
    **Why?** Provides a consistent way to quickly find a specific file using an editor or IDE's fuzzy search techniques.
    
    **为什么？** 体统一个统一的方法，利用一个编辑器或者IDE的来快速的模糊搜索技巧，快速找到一个特定文件。

.s-why.s-why-last
  :marked
    **Why?** Provides pattern matching for any automated tasks.
    
    **为什么？** 为任何自动任务提供一个模式配对。

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.l-main-section
:marked
  ### Components and Directives
  ### 组件和指令
  <a id="02-03"></a>
  #### Style 02-03
  #### 风格02-03

.s-rule.do
  :marked
    **Do** use consistent names for all assets named after what they represent.
<<<<<<< HEAD
    **做** 为所有东西使用统一的命名：以它们所代表的东西命名
=======
    **做** 为所有财产的使用统一的命名：以它们所代表的东西命名
>>>>>>> f0e75413c854b8966c506c7c351339c9f5e98512

.s-rule.do
  :marked
    **Do** use upper camel case for symbols. Match the name of the symbol to the naming of the file.
    
    **做** 使用大写驼峰命名法来命名所有符号（类）。配对符号的名字和它所在的文件名字。

.s-rule.do
  :marked
    **Do** append the symbol name with the suffix that it represents.
    
    **做** 把符号所代表的（比如组件、服务、指令等）附加到符号名字右面。
  

.s-why
  :marked
    **Why?** Provides a consistent way to quickly identify and reference assets.
    
    **为什么？** 提供一个前后一致的方法，用来迅速辨识和引用东西。

.s-why
  :marked
    **Why?** Upper camel case is conventional for identifying objects that can be instantiated using a constructor.
    
    **为什么？** 使用大写驼峰命名法是一个辨识可以使用构造函数来实例化的对象的常规。
    
.s-why.s-why-last
  :marked
    **Why?** The `Component` suffix is more commonly used and is more explicitly descriptive.
    
    **为什么？** `Component`后缀是更加常见的用法，它具有精准的描述性。

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%")
  tr
    th Symbol Name
    th File Name
  tr(style=top)
    td
      code-example.
        @Component({ ... })
        export class AppComponent {}
    td
      :marked
        app.component.ts
  tr(style=top)
    td
      code-example.
        @Component({ ... })
        export class HeroesComponent
    td
      :marked
        heroes.component.ts
  tr(style=top)
    td
      code-example.
        @Component({ ... })
        export class HeroListComponent
    td
      :marked
        hero-list.component.ts
  tr(style=top)
    td
      code-example.
        @Component({ ... })
        export class HeroDetailComponent
    td
      :marked
        hero-detail.component.ts
  tr(style=top)
    td
      code-example.
        @Directive({ ... })
        export class ValidationDirective
    td
      :marked
        validation.directive.ts
:marked

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.l-main-section
:marked
  ### Service Names
  
  ### 服务名字
  <a id="02-04"></a>
  #### Style 02-04
  
  #### 风格02-04

.s-rule.do
  :marked
    **Do** use consistent names for all services named after their feature.
    
    **做** 为所有服务使用前后一致的命名规则，以它们的特性来命名。

.s-rule.do
  :marked
    **Do** use upper camel case for services.
    
    **做** 使用大写驼峰命名法来命名服务。

.s-rule.do
  :marked
    **Do** suffix services with `Service` when it is not clear what they are (e.g. when they are nouns).
    
    **做** 当不是很清楚它们是什么的时候（比如它们为名词时），添加`Service`后缀。

.s-why
  :marked
    **Why?** Provides a consistent way to quickly identify and reference services.
    
    **为什么？** 提供一个前后统一的方法来快速识别和引用服务。

.s-why
  :marked
    **Why?** Clear service names such as `logger` do not require a suffix.
    
    **为什么？** 清楚的服务名字比如`logger`不需要一个后缀。

.s-why.s-why-last
  :marked
    **Why?** Service names such as `Credit` are nouns and require a suffix and should be named with a suffix when it is not obvious if it is a service or something else.
    
    **为什么？** 服务名字比如`Credit`是名词，需要一个后缀，当不是很明显它是一个服务还是其他东西的时候，取名时应该跟上后缀。

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%")
  tr
    th Symbol Name
    th File Name
  tr(style=top)
    td
      code-example.
        @Injectable()
        export class HeroDataService {}
    td
      :marked
        hero-data.service.ts
  tr(style=top)
    td
      code-example.
        @Injectable()
        export class CreditService {}
    td
      :marked
        credit.service.ts
  tr(style=top)
    td
      code-example.
        @Injectable()
        export class LoggerService {}
    td
      :marked
        logger.service.ts
:marked

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.l-main-section
:marked
  ### Bootstrapping
  ### 引导程序
  <a id="02-05"></a>
  #### Style 02-05
  #### 风格02-05

.s-rule.do
  :marked
    **Do** put bootstrapping and platform logic for the app in a file named `main.ts`.
    
    **做** 把应用程序的引导程序和平台逻辑放到一个名字为`main.ts`的文件里。

.s-rule.avoid
  :marked
    **Avoid** putting app logic in the `main.ts`. Instead consider placing it in a Component or Service.
    
    **避免** 把应用程序逻辑放到`main.ts`里。而是考虑把它放到一个组件或服务里面。

.s-why
  :marked
    **Why?** Follows a consistent convention for the startup logic of an app.
    
    **为什么？** 遵循一个前后统一的规则来命名应用程序的启动逻辑。

.s-why.s-why-last
  :marked
    **Why?** Follows a familiar convention from other technology platforms.
    
    **为什么？** 从其他技术平台借鉴一个熟悉的命名规则。

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:marked
  ### Directive Selectors
  ### 指令选择器
  <a id="02-06"></a>
  #### Style 02-06
  #### 风格02-06

.s-rule.do
  :marked
    **Do** Use lower camel case for naming the selectors of our directives.
    
    **做** 使用小驼峰命名法来命名指令的选择器。

.s-why
  :marked
    **Why?** Keeps the names of the properties defined in the directives that are bound to the view consistent with the attribute names.
    
    **为什么？** 保持指令里定义的属性名字与他们绑定的视图的HTML属性名字一致。

.s-why.s-why-last
  :marked
    **Why?** The Angular 2 HTML parser is case sensitive and will recognize lower camel case.
    
    **为什么？** Angular 2 HTML剖析器是大小写敏感的，而且它识别小写驼峰写法。

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:marked
  ### Custom Prefix for Components
  ### 为组件自定义前缀
  <a id="02-07"></a>
  #### Style 02-07
  #### 风格02-07

.s-rule.do
  :marked
    **Do** use a custom prefix for the selector of our components. For example, the prefix `toh` represents from **T**our **o**f **H**eroes and the prefix `admin` represents an admin feature area.
    
    **做** 为组件的选择器使用一个自定义前缀。比如，前缀`tod`是从**T**our **o**f **H**eros来的，前缀`admin`代表了admin的特征区域。

.s-rule.do
  :marked
    **Do** use a prefix that identifies the feature area or the app itself.
    
    **做** 使用一个前缀来识别特征区域或者应用程序本身。

.s-why
  :marked
    **Why?** Prevents name collisions.
    
    **为什么？** 防止名字冲突。

.s-why
  :marked
    **Why?** Makes it easier to promote and share our feature in other apps.
    
    **为什么？** 让在其他程序里面促销和共享我们的特性变得更加容易。

.s-why.s-why-last
  :marked
    **Why?** Our Components and elements are easily identified.
    
    **为什么？** 我们的组件和元素更加容易被识别出来。

+makeExample('style-guide/ts/02-07/app/heroes/hero.component.avoid.ts', 'example', 'app/heroes/hero.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/02-07/app/users/users.component.avoid.ts', 'example', 'app/users/users.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/02-07/app/heroes/hero.component.ts', 'example', 'app/heroes/hero.component.ts')
:marked

+makeExample('style-guide/ts/02-07/app/users/users.component.ts', 'example', 'app/users/users.component.ts')
:marked

:marked
  ### Custom Prefix for Directives
  ### 为指令自定义前缀
  <a id="02-08"></a>
  #### Style 02-08
  #### 风格02-08

.s-rule.do
  :marked
    **Do** use a custom prefix for the selector of our directives (for instance below we use the prefix `toh` from **T**our **o**f **H**eroes).
    
    **做** 为指令的选择器使用一个自定义的前缀（比如下面例子用，我们使用前缀`toh`，取自**T**our **o**f **H**eroes)。

.s-why
  :marked
    **Why?** Prevents name collisions.
    
    **为什么？** 防止名字冲突。

.s-why.s-why-last
  :marked
    **Why?** Our Directives are easily identified.
    
    **为什么？** 指令更加容易被识别。

+makeExample('style-guide/ts/02-08/app/shared/validate.directive.avoid.ts', 'example', 'app/shared/validate.directive.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/02-08/app/shared/validate.directive.ts', 'example', 'app/shared/validate.directive.ts')
:marked

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.l-main-section
:marked
  ### Pipe Names
  ### 管道名字
  <a id="02-09"></a>
  #### Style 02-09
  #### 风格02-09

.s-rule.do
  :marked
    **Do** use consistent names for all pipes, named after their feature.
    
    **做** 为所有管道使用前后一致的命名规则，用它们的特性来命名。

.s-why.s-why-last
  :marked
    **Why?** Provides a consistent way to quickly identify and reference pipes.
    
    **为什么？** 提供一个一致的方法快速识别和引用管道。

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%")
  tr
    th Symbol Name
    th File Name
  tr(style=top)
    td
      code-example.
        @Pipe({ name: 'ellipsis' })
        export class EllipsisPipe implements PipeTransform { }
    td
      :marked
        ellipsis.pipe.ts
  tr(style=top)
    td
      code-example.
        @Pipe({ name: 'initCaps' })
        export class InitCapsPipe implements PipeTransform { }
    td
      :marked
        init-caps.pipe.ts
:marked

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.l-main-section
:marked
  ### Unit Test File Names
  ### 单元测试文明命名
  <a id="02-10"></a>
  #### Style 02-10
  #### 风格02-10

.s-rule.do
  :marked
    **Do** name test specification files the same as the component they test.
    
    **做** 测试配置文件的取名应该和被测试的组件名字一样。

.s-rule.do
  :marked
    **Do** name test specification files with a suffix of `.spec`.
    
    **做** 测试配置文件命名应该跟随后缀`.spec`。

.s-why
  :marked
      **Why?** Provides a consistent way to quickly identify tests.
      
      **为什么？** 提供一个统一的方法来快速识别测试。

.s-why.s-why-last
  :marked
      **Why?** Provides pattern matching for [karma](http://karma-runner.github.io/) or other test runners.
      
      **为什么？** 提供一个与[karma](http://karma-runner.github.io/)或者其他测试运行器相配的命名模式。

:marked
- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%")
  tr
    th Symbol Name
    th File Name
  tr(style=top)
    td
      :marked
        Components
    td
      :marked
        heroes.component.spec.ts
      :marked
        hero-list.component.spec.ts
      :marked
        hero-detail.component.spec.ts
  tr(style=top)
    td
      :marked
        Services
    td
      :marked
        logger.service.spec.ts
      :marked
        hero.service.spec.ts
      :marked
        filter-text.service.spec.ts
  tr(style=top)
    td
      :marked
        Pipes
    td
      :marked
        ellipsis.pipe.spec.ts
      :marked
        init-caps.pipe.spec.ts
:marked

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.l-main-section
:marked
  ### End to End Test File Names
  ### 端对端测试文件名字
  <a id="02-11"></a>
  #### Style 02-11
  #### 风格02-11

.s-rule.do
  :marked
    **Do** name end-to-end test specification files after the feature they test with a suffix of `.e2e-spec`.
    
    **做** 端对端测试配置文件应该和它们所测试的特征同名，并加上后缀`.e2e-spec`。

.s-why
  :marked
    **Why?** Provides a consistent way to quickly identify end-to-end tests.
    
    *为什么？** 提供一个统一的方法快速识别端对端测试文件。

.s-why.s-why-last
  :marked
    **Why?** Provides pattern matching for test runners and build automation.
    
    **为什么？** 提供一个模式，与测试运行器和自动建造相配。

:marked
:marked
- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%")
  tr
    th Symbol Name
    th File Name
  tr(style=top)
    td
      :marked
        End to End Tests
    td
      :marked
        app.e2e-spec.ts
      :marked
        heroes.e2e-spec.ts
:marked

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.l-main-section
:marked
  ## Coding Conventions
  ## 代码规则

  Have consistent set of coding, naming, and whitespace conventions.
  
  采用一套前后一致的编码、命名和空格的规则。

.l-main-section
:marked
  ### Classes
  ### 类
  <a id="03-01"></a>
  #### Style 03-01
  #### 风格03-01

.s-rule.do
  :marked
    **Do** use upper camel case when naming classes.
    
    **做** 使用大写驼峰命名法来命名类。

.s-why
  :marked
    **Why?** Follows conventional thinking for class names.
    
    **为什么？** 遵循类命名传统规则。

.s-why.s-why-last
  :marked
    **Why?** Classes can be instantiated and construct an instance. We often use upper camel case to indicate a constructable asset.
    
    **为什么？** 类是可以被实例化并建造一个实例的。我们通常使用大写驼峰命名规则来标示一个可以建造的东西。

+makeExample('style-guide/ts/03-01/app/shared/exception.service.avoid.ts', 'example', 'app/shared/exception.service.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/03-01/app/shared/exception.service.ts', 'example', 'app/shared/exception.service.ts')
:marked

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.l-main-section
:marked
  ### Constants
  ### 常量
  <a id="03-02"></a>
  #### Style 03-02
  #### 风格03-02

.s-rule.do
  :marked
    **Do** use uppercase with underscores when naming constants.
    
    **做** 使用全大写，用下划线隔开的方法来命名常量。

.s-why
  :marked
    **Why?** Follows conventional thinking for constants.
    
    **为什么？** 遵循传统的命名常量的方法。

.s-why.s-why-last
  :marked
    **Why?** Constants can easily be identified.
    
    **为什么？** 常量可以很容易的被识别。

+makeExample('style-guide/ts/03-02/app/shared/data.service.avoid.ts', 'example', 'app/shared/data.service.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/03-02/app/shared/data.service.ts', 'example', 'app/shared/data.service.ts')
:marked

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.l-main-section
:marked
  ### Interfaces
  ### 接口
  <a id="03-03"></a>
  #### Style 03-03
  #### 风格03-03

.s-rule.do
  :marked
    **Do** name an interface using upper camel case.
    
    **做** 使用大写驼峰命名法来命名接口。

.s-rule.do
  :marked
    **Consider** naming an interface without an `I` prefix.
    
    **考虑** 不要在接口名字前面家`T`前缀。

.s-why.s-why-last
  :marked
    **Why?** When we use types, we can often simply use the class as the type.
    
    **为什么？** 当我们使用类型时，我们可以经常简单地使用类来作为类型。

+makeExample('style-guide/ts/03-03/app/shared/hero-collector.service.avoid.ts', 'example', 'app/shared/hero-collector.service.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/03-03/app/shared/hero-collector.service.ts', 'example', 'app/shared/hero-collector.service.ts')
:marked

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.l-main-section
:marked
  ### Properties and Methods
  ### 属性和方法
  <a id="03-04"></a>
  #### Style 03-04
  #### 风格03-04

.s-rule.do
  :marked
    **Do** use lower camel case to name properties and methods.
    
    **做** 使用小写驼峰命名法来命名属性和方法。

.s-rule.avoid
  :marked
    **Avoid** prefixing private properties and methods with an underscore.
    
    **避免** 使用下划线为前缀来命名私有属性和方法。

.s-why
  :marked
    **Why?** Follows conventional thinking for properties and methods.
    **为什么？** 遵循传统的命名属性和方法的规则。

.s-why
  :marked
    **Why?** JavaScript lacks a true private property or method.
    
    **为什么？** JavaScript不支持真正的私有属性和方法。

.s-why.s-why-last
  :marked
    **Why?** TypeScript tooling makes it easy to identify private vs public properties and methods.
    
    **为什么？** TypeScript工具使识别私有或公有属性和方法变得很简单。

+makeExample('style-guide/ts/03-04/app/shared/toast/toast.service.avoid.ts', 'example', 'app/shared/toast/toast.service.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/03-04/app/shared/toast/toast.service.ts', 'example', 'app/shared/toast/toast.service.ts')
:marked

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.l-main-section
:marked
  ### Import Destructuring Spacing
  ### 导入声明解构空格
  <a id="03-05"></a>
  #### Style 03-05
  #### 风格03-05

.s-rule.do
  :marked
    **Do** leave one whitespace character inside of the `import` statements' curly braces when destructuring.
    
    **做** 在解构是，`import`声明的大括号里面留一个空格字符。

.s-why.s-why-last
  :marked
    **Why?** Whitespace makes it easier to read the imports.
    
    **为什么？** 空格让导入声明更容易阅读。

+makeExample('style-guide/ts/03-05/app/+heroes/shared/hero.service.avoid.ts', 'example', 'app/+heroes/shared/hero.service.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/03-05/app/+heroes/shared/hero.service.ts', 'example', 'app/+heroes/shared/hero.service.ts')
:marked

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.l-main-section
:marked
  ### Import Line Spacing
  ### 导入声明空行
  <a id="03-06"></a>
  #### Style 03-06
  #### 风格03-06

.s-rule.do
  :marked
    **Do** leave one empty line between third party imports and imports of code we created.
    
    **做** 在第三方导入和自己创建的代码导入之间留一个空行。

.s-rule.do
  :marked
    **Do** list import lines alphabetized by the module.
    
    **做** 按模块名字的字母顺排列导入行。

.s-rule.do
  :marked
    **Do** list destructured imported assets alphabetically.
    
    **做** 按字母顺序排列解构导入行。

.s-why
  :marked
    **Why?** The empty line makes it easy to read and locate imports.
    
    **为什么？** 空行可以让阅读和定位本地导入变得更加容易。

.s-why.s-why-last
  :marked
    **Why?** Alphabetizing makes it easier to read and locate imports.
    
    **为什么？** 按字母顺序排列可以让阅读和定位本地导入更加容易。

+makeExample('style-guide/ts/03-06/app/+heroes/shared/hero.service.avoid.ts', 'example', 'app/+heroes/shared/hero.service.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/03-06/app/+heroes/shared/hero.service.ts', 'example', 'app/+heroes/shared/hero.service.ts')
:marked

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.l-main-section
:marked
  ## Application Structure
  ## 应用程序结构

  Have a near term view of implementation and a long term vision. Start small but keep in mind where the app is heading down the road.
  
  准备一个短期的执行方案和一个长期的执行方案。从零开始，但是时刻考虑应用程序接下来要走的路。

  All of the app's code goes in a folder named `app`. All content is 1 feature per file. Each component, service, and pipe is in its own file. All 3rd party vendor scripts are stored 
  in another folder and not in the `app` folder. We didn't write them and we don't want them cluttering our app. Use the naming conventions for files in this guide.
  
  把所有的应用程序源代码都放到一个名叫`app`的目录里。所有内容都遵循一个特征一个文件。每个组件、服务和管道都在自己的文件里。所有第三方程序包都被保存到其他目录里，并确保不在`app`目录里。
  我们不会修改他们，所以我们不希望他们弄乱我们的应用程序。使用本指南介绍的文件命名规则。

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.l-main-section
:marked
  ### LIFT
  ### LIFT (定位`L`ocate、识别`I`dentity、平坦`F`lattest、尝试`T`ry遵循不重复自己DRY - Do Not Repeat Yourself规则)
  <a id="04-01"></a>
  #### Style 04-01
  #### 风格04-01

.s-rule.do
  :marked
    **Do** structure the app such that we can `L`ocate our code quickly, `I`dentify the code at a glance, keep the `F`lattest structure we can, and `T`ry to be DRY.
    
    **做** 组织应用程序的结构，达到这些目的：快速定位(`L`ocate)代码、一眼识别(`I`dentify)代码、尽量保持结构平坦(`F`lattest)和尝试`T`ry遵循不重复自己DRY - Do Not Repeat Yourself规则。

.s-rule.do
  :marked
    **Do** define the structure to follow these four basic guidelines, listed in order of importance.
    
    **做** 按照下面按照重要顺序列出的四个基本原则来定义结构。

.s-why.s-why-last
  :marked
    **Why?** LIFT Provides a consistent structure that scales well, is modular, and makes it easier to increase developer efficiency by finding code quickly. 
    Another way to check our app structure is to ask ourselves: How quickly can we open and work in all of the related files for a feature?
    
    **为什么？** LIFT提供了一个前后一致的结构，它扩展行强，模块化，并且因为能快速找到代码，让提高开发者效率变得更加容易。另外一个检查应用程序结构的方法是质问自己：我们打开和编辑一个特征相关的所有文件的速度如何？

a(href="#toc") Back to top

.l-main-section
:marked
  ### Locate
  ### 定位
  <a id="04-02"></a>
  #### Style 04-02
  #### 风格04-02

.s-rule.do
  :marked
    **Do** make locating our code intuitive, simple and fast.
    
    **做** 直观、简单和快速的定位我们的代码。

.s-why.s-why-last
  :marked
    **Why?** We find this to be super important for a project. If we cannot find the files we need to work on quickly, we will not be able to work as efficiently as possible, 
    and the structure needs to change. We may not know the file name or where its related files are, so putting them in the most intuitive locations and near each other saves a ton of time. 
    A descriptive folder structure can help with this.
    
    **为什么？** 我们发现定位对一个项目是非常重要的。如果我们不能快速找到需要工作的文件，我们就不能再最佳效率状态下面工作，结构就需要更换。我们可能不知道文件的名称或者文件所在目录，所以
    我们把它们放到一个直观的地方，一个挨着一个，可以节省很多时间。采用一个说明性强的文件结构能够帮忙解决该问题。

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.l-main-section
:marked
  ### Identify
  ### 识别
  <a id="04-03"></a>
  #### Style 04-03
  #### 风格04-03

.s-rule.do
  :marked
    **Do** name the file such that we instantly know what it contains and represents.
    
    **做** 命名文件到这个程度：可以立刻知道它包含了什么，代表了什么。

.s-rule.do
  :marked
    **Do** be descriptive with file names and keeping the contents of the file to exactly one component.
    
    **做** 文件名要具有说明性，并保存文件内容只包含一个组件。

.s-rule.avoid
  :marked
    **Avoid** files with multiple components, multiple services, or a mixture.
    
    **避免** 包含很多组件、服务或者混合的文件。

.s-why.s-why-last
  :marked
    **Why?** We spend less time hunting and pecking for code, and become more efficient. If this means we want longer file names, then so be it.
    **为什么？** 我们花费更少的时间来查找和琢磨代码，变得更加有效率。如果这意味着更长的文件名，那就让它去吧。

.l-sub-section
  :marked
    There are deviations of the 1 per file rule when we have a set of very small features that are all related to each other, as they are still easily identifiable.
    
    当我们有一套非常小并且互相关联的特征时，我们可能不采用单文件单组件的规则，因为他们还是非常容易被识别。

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.l-main-section
:marked
  ### Flat
  ### 平坦
  <a id="04-04"></a>
  #### Style 04-04
  #### 风格04-04

.s-rule.do
  :marked
    **Do** keep a flat folder structure as long as possible.
    
    **做** 尽可能保持一个平坦的目录结构。

.s-rule.consider
  :marked
    **Consider** creating fodlers when we get to seven or more files.
    
    **考虑** 当我们有7个或更多的文件时才新建目录。

.s-why.s-why-last
  :marked
    **Why?** Nobody wants to search seven levels of folders to find a file. In a folder structure there is no hard and fast number rule, but when a folder has seven to ten files, 
    that may be time to create subfolders. We base it on our comfort level. Use a flatter structure until there is an obvious value (to help the rest of LIFT) in creating a new folder.
    
    **为什么？** 没有人愿意搜索7层目录来找一个文件。在一个目录结构中，没有一个硬数字规则，但是当一个文件有七到十个文件时，就是需要新建子目录的时候了。这是基于舒适级别来定的。
    以一个平坦结构未开始，知道有很明显的价值来新建目录（来配合其他LIFT规则）

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.l-main-section
:marked
  ### T-DRY (Try to be DRY)
  ### T-DRY （尝试遵循不重复自己DRY的规则）
  <a id="04-05"></a>
  #### Style 04-05
  #### 风格04-05

.s-rule.do
  :marked
    **Do** be DRY (Don't Repeat Yourself)
    
    **做** 不要重复自己（DRY）

.s-rule.avoid
  :marked
    **Avoid** being so DRY that we sacrifice readability.
    
    **避免** 过度DRY，以致牺牲了阅读性。

.s-why.s-why-last
  :marked
    **Why?** Being DRY is important, but not crucial if it sacrifices the others in LIFT, which is why we call it T-DRY. We don’t want to type `hero-view.component.html` for a view because, 
    well, it’s obviously a view. If it is not obvious or by convention, then we name it.
    
    **为什么？** 不重复自己很重要，但是如果它要牺牲其他的LIFT规则，它不是最重要的，这就是为什么我们叫做**尝试**不重复自己(T-DRY)。我们不愿意为了一个试图敲打`hero-view.component.html`，因为它很明显是一个试图。
    如果它不是很明显是一个试图，那么我们就把视图单词加到它的名字里。

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.l-main-section
:marked
  ### Overall Structural Guidelines
  ### 总体结构原则
  <a id="04-06"></a>
  #### Style 04-06
  #### 风格04-06

.s-rule.do
  :marked
    **Do** start small but keep in mind where the app is heading down the road.
    
    **坐** 从零开始，但是时刻考虑应用程序接下来要走的路。

.s-rule.do
  :marked
    **Do** have a near term view of implementation and a long term vision.
    
    **做** 有一个短期的执行方案和一个长期的执行方案。

.s-rule.do
  :marked
    **Do** put all of the app's code in a folder named `app`.
    
    **做** 把所有源代码都放到名为`app`的目录里。

.s-rule.consider
  :marked
    **Consider** creating a folder for each component including its `.ts`, `.html`, `.css` and `.spec` file.
    
    **考虑**

.s-why
  :marked
    **Why?** Helps us keep the app structure small and easy to maintain in the early stages, while being easy to evolve as the app grows.

.s-why.s-why-last
  :marked
    **Why?** Components often have four files (e.g. `*.html`, `*.css`, `*.ts`, and `*.spec.ts`) and can clutter a folder quickly.

.example-title Overall Folder and File Structure
.filetree
  .file src
  .children
    .file app
    .children
      .file +heroes
      .children
        .file hero
        .children
          .file hero.component.ts|html|css|spec.ts
          .file index.ts
        .file hero-list
        .children
          .file hero-list.component.ts|html|css|spec.ts
          .file index.ts
        .file shared
        .children
          .file hero.model.ts
          .file hero.service.ts|spec.ts
          .file index.ts
        .file heroes.component.ts|html|css|spec.ts
        .file index.ts
      .file shared
      .children
        .file ...
      .file app.component.ts|html|css|spec.ts
      .file main.ts
    .file index.html
    .file ...
:marked

.l-sub-section
  :marked
    While we prefer our Components to be in their own dedicated folder, another option for small apps is to keep Components flat (not in a dedicated folder). This adds up to four files to the existing folder, but also reduces the folder nesting. Be consistent.

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.l-main-section
:marked
  ### Shared Folder
  <a id="04-07"></a>
  #### Style 04-07

.s-rule.do
  :marked
    **Do** put all shared files within a component feature in a `shared` folder.

.s-rule.consider
  :marked
    **Consider** creating a folder for each component including its `.ts`, `.html`, `.css` and `.spec` file.

.s-why
  :marked
    **Why?** Separates shared files from the components within a feature.

.s-why.s-why-last
  :marked
    **Why?** Makes it easier to locate shared files within a component feature.

.example-title Shared Folder
.filetree
  .file src
  .children
    .file app
    .children
      .file +heroes
      .children
        .file hero
        .children
          .file ...
        .file hero-list
        .children
          .file ...
        .file shared
        .children
          .file hero-button
          .children
            .file ...
          .file hero.model.ts
          .file hero.service.ts|spec.ts
          .file index.ts
        .file heroes.component.ts|html|css|spec.ts
        .file index.ts
      .file shared
      .children
        .file exception.service.ts|spec.ts
        .file index.ts
        .file nav
        .children
          .file ...
      .file app.component.ts|html|css|spec.ts
      .file main.ts
    .file index.html
    .file ...
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Folders-by-Feature Structure
  <a id="04-08"></a>
  #### Style 04-08

.s-rule.do
  :marked
    **Do** create folders named for the feature they represent.

.s-why
  :marked
    **Why?** A developer can locate the code, identify what each file represents at a glance, the structure is as flat as it can be, and there is no repetitive nor redundant names.

.s-why
  :marked
    **Why?** The LIFT guidelines are all covered.

.s-why
  :marked
    **Why?** Helps reduce the app from becoming cluttered through organizing the content and keeping them aligned with the LIFT guidelines.

.s-why.s-why-last
  :marked
    **Why?** When there are a lot of files (e.g. 10+) locating them is easier with a consistent folder structures and more difficult in flat structures.

:marked
  Below is an example of a small app with folders per component.

.example-title Folders per Component
.filetree
  .file src
  .children
    .file app
    .children
      .file +heroes
      .children
        .file hero
        .children
          .file ...
        .file hero-list
        .children
          .file ...
        .file shared
        .children
          .file ...
        .file heroes.component.ts|html|css|spec.ts
        .file index.ts
      .file +villains
      .children
        .file villain
        .children
          .file ...
        .file villain-list
        .children
          .file ...
        .file shared
        .children
          .file ...
        .file villains.component.ts|html|css|spec.ts
        .file index.ts
      .file shared
      .children
        .file nav
        .children
          .file ...
        .file ...
      .file app.component.ts|html|css|spec.ts
      .file main.ts
    .file index.html
    .file ...
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Layout Components
  <a id="04-09"></a>
  #### Style 04-09

.s-rule.do
  :marked
    **Do** put components that define the overall layout in a `shared` folder.

.s-rule.do
  :marked
    **Do** put shared layout components in their own folder, under the `shared` folder.

.s-why
  :marked
    **Why?** We need a place to host our layout for our app. Our navigation bar, footer, and other aspects of the app that are needed for the entire app.

.s-why.s-why-last
  :marked
    **Why?** Organizes all layout in a consistent place re-used throughout the application.

.example-title Folder for Layout Components
.filetree
  .file src
  .children
    .file app
    .children
      .file +heroes
      .children
        .file ...
      .file shared
      .children
        .file nav
        .children
          .file index.ts
          .file nav.component.ts|html|css|spec.ts
        .file footer
        .children
          .file index.ts
          .file footer.component.ts|html|css|spec.ts
        .file index.ts
        .file ...
      .file app.component.ts|html|css|spec.ts
      .file main.ts
    .file index.html
    .file ...
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Create and Import Barrels
  <a id="04-10"></a>
  #### Style 04-10

.s-rule.do
  :marked
    **Do** create a file that imports, aggregates, and re-exports items. We call this technique a **barrel**.

.s-rule.do
  :marked
    **Do** name this barrel file `index.ts`.

.s-why
  :marked
    **Why?** A barrel aggregates many imports into a single import.

.s-why
  :marked
    **Why?** A barrel reduces the number of imports a file may need.

.s-why.s-why-last
  :marked
    **Why?** A barrel shortens import statements.

+makeTabs(
  `style-guide/ts/04-10/app/shared/index.ts,
  style-guide/ts/04-10/app/shared/filter-text/index.ts,
  style-guide/ts/04-10/app/shared/modal/index.ts,
  style-guide/ts/04-10/app/shared/nav/index.ts,
  style-guide/ts/04-10/app/shared/spinner/index.ts,
  style-guide/ts/04-10/app/shared/toast/index.ts`,
  `example,,,,,`,
  `app/shared/index.ts,
  app/shared/filter-text/index.ts,
  app/shared/modal/index.ts,
  app/shared/nav/index.ts,
  app/shared/spinner/index.ts,
  app/shared/toast/index.ts`)
:marked

.example-title Folder Barrels
.filetree
  .file src
  .children
    .file app
    .children
      .file +dashboard
      .children
        .file ...
        .file index.ts
      .file +heroes
      .children
        .file ...
        .file index.ts
      .file shared
      .children
        .file nav
        .children
          .file ...
          .file index.ts
        .file search
        .children
          .file ...
          .file index.ts
        .file ...
        .file index.ts
      .file app.component.ts|html|css|spec.ts
      .file main.ts
    .file index.html
    .file ...
:marked

+makeExample('style-guide/ts/04-10/app/+heroes/heroes.component.avoid.ts', 'example', 'app/+heroes/heroes.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/04-10/app/+heroes/heroes.component.ts', 'example', 'app/+heroes/heroes.component.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Lazy Loaded Folders
  <a id="04-11"></a>
  #### Style 04-11
  A distinct application feature or workflow may be *lazy loaded* or *loaded on demand* rather than when the application starts.

.s-rule.do
  :marked
    **Do** put the contents of lazy loaded features in a *lazy loaded folder*.
    A typical *lazy loaded folder* contains a *routing component*, its child components, and their related assets and modules.

.s-why.s-why-last
  :marked
    **Why?** The folder makes it easy to identify and isolate the feature content.

a(href="#toc") Back to top

.l-main-section
:marked
  ### Prefix Lazy Loaded Folders with +
  <a id="04-12"></a>
  #### Style 04-12

.s-rule.do
  :marked
    **Do** prefix the name of a *lazy loaded folder* with a (+) e.g., `+dashboard/`.

.s-why
  :marked
    **Why?** Lazy loaded code paths are easily identifiable by their `+` prefix.

.s-why
  :marked
    **Why?** Lazy loaded code paths are easily distinguishable from non lazy loaded paths.

.s-why.s-why-last
  :marked
    **Why?** If we see an `import` path that contains a `+`, we can quickly refactor to use lazy loading.

.example-title Lazy Loaded Folders
.filetree
  .file src
  .children
    .file app
    .children
      .file +dashboard
      .children
        .file dashboard.component.ts|html|css|spec.ts
        .file index.ts
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Never Directly Import Lazy Loaded Folders
  <a id="04-13"></a>
  #### Style 04-13

.s-rule.avoid
  :marked
    **Avoid** allowing modules in sibling and parent folders to directly import a module in a *lazy loaded feature*.

.s-why.s-why-last
  :marked
    **Why?** Directly importing a module loads it immediately when our intention is to load it on demand.

+makeExample('style-guide/ts/04-13/app/app.component.avoid.ts', 'example', 'app/app.component.ts')(avoid=1)
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Lazy Loaded Folders May Import From a Parent
  <a id="04-14"></a>
  #### Style 04-14

.s-rule.do
  :marked
    **Do** allow lazy loaded modules to import a module from a parent folder.

.s-why.s-why-last
  :marked
    **Why?** A parent module has already been loaded by the time the lazy loaded module imports it.

+makeExample('style-guide/ts/04-14/app/heroes/heroes.component.ts', 'example', 'app/heroes/heroes.component.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Use Component Router to Lazy Load
  <a id="04-15"></a>
  #### Style 04-15

.s-rule.do
  :marked
    **Do** use the Component Router to lazy load routable features.

.s-why.s-why-last
  :marked
    **Why?** That's the easiest way to load a module on demand.

a(href="#toc") Back to top

.l-main-section
:marked
  ## Components

  ### Components Selector Naming
  <a id="05-02"></a>
  #### Style 05-02

.s-rule.do
  :marked
    **Do** use `kebab-case` for naming the element selectors of our components.

.s-why.s-why-last
  :marked
    **Why?** Keeps the element names consistent with the specification for [Custom Elements](https://www.w3.org/TR/custom-elements/).

+makeExample('style-guide/ts/05-02/app/heroes/shared/hero-button/hero-button.component.avoid.ts', 'example', 'app/heroes/shared/hero-button/hero-button.component.ts')(avoid=1)
:marked

+makeTabs(
  `style-guide/ts/05-02/app/heroes/shared/hero-button/hero-button.component.ts,
  style-guide/ts/05-02/app/app.component.html`,
  'example,',
  `app/heroes/shared/hero-button/hero-button.component.ts,
  app/app.component.html`)
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Components as Elements
  <a id="05-03"></a>
  #### Style 05-03

.s-rule.do
  :marked
    **Do** define Components as elements via the selector.

.s-why
  :marked
    **Why?** Components have templates containing HTML and optional Angular template syntax. They are most associated with putting content on a page, and thus are more closely aligned with elements.

.s-why
  :marked
    **Why?** Components are derived from Directives, and thus their selectors can be elements, attributes, or other selectors. Defining the selector as an element provides consistency for components that represent content with a template.

.s-why.s-why-last
  :marked
    **Why?** It is easier to recognize that a symbol is a component vs a directive by looking at the template's html.

+makeExample('style-guide/ts/05-03/app/heroes/shared/hero-button/hero-button.component.avoid.ts', 'example', 'app/heroes/hero-button/hero-button.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/05-03/app/heroes/shared/hero-button/hero-button.component.avoid.html', '', 'app/heroes/hero-button/hero-button.component.html')(avoid=1)
:marked

+makeTabs(
  `style-guide/ts/05-03/app/heroes/shared/hero-button/hero-button.component.ts,
  style-guide/ts/05-03/app/app.component.html`,
  'example,',
  `app/heroes/shared/hero-button/hero-button.component.ts,
  app/app.component.html`)
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Extract Template and Styles to Their Own Files
  <a id="05-04"></a>
  #### Style 05-04

.s-rule.do
  :marked
    **Do** extract templates and styles into a separate file, when more than 3 lines.

.s-rule.do
  :marked
    **Do** name the template file `[component-name].component.html`, where [component-name] is our component name.

.s-rule.do
  :marked
    **Do** name the style file `[component-name].component.css`, where [component-name] is our component name.

.s-why
  :marked
    **Why?** Syntax hints for inline templates in (*.js and *.ts) code files are not supported by some editors.

.s-why.s-why-last
  :marked
    **Why?** A component file's logic is easier to read when not mixed with inline template and styles.

+makeExample('style-guide/ts/05-04/app/heroes/heroes.component.avoid.ts', 'example', 'app/heroes/heroes.component.ts')(avoid=1)
:marked

+makeTabs(
  `style-guide/ts/05-04/app/heroes/heroes.component.ts,
  style-guide/ts/05-04/app/heroes/heroes.component.html,
  style-guide/ts/05-04/app/heroes/heroes.component.css`,
  'example,,',
  `app/heroes/heroes.component.ts,
  app/heroes/heroes.component.html,
  app/heroes/heroes.component.css`)
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Decorate Input and Output Properties Inline
  <a id="05-12"></a>
  #### Style 05-12

.s-rule.do
  :marked
    **Do** use [`@Input`](https://angular.io/docs/ts/latest/api/core/Input-var.html) and [`@Output`](https://angular.io/docs/ts/latest/api/core/Output-var.html) instead of the `inputs` and `outputs` properties of the [`@Directive`](https://angular.io/docs/ts/latest/api/core/Directive-decorator.html) and [`@Component`](https://angular.io/docs/ts/latest/api/core/Component-decorator.html) decorators:

.s-rule.do
  :marked
    **Do** place the `@Input()` or `@Output()` on the same line as the property they decorate.

.s-why
  :marked
    **Why?** It is easier and more readable to identify which properties in a class are inputs or outputs.

.s-why
  :marked
    **Why?** If we ever need to rename the property or event name associated to [`@Input`](https://angular.io/docs/ts/latest/api/core/Input-var.html) or [`@Output`](https://angular.io/docs/ts/latest/api/core/Output-var.html) we can modify it on a single place.

.s-why
  :marked
    **Why?** The metadata declaration attached to the directive is shorter and thus more readable.

.s-why.s-why-last
  :marked
    **Why?** Placing the decorator on the same line makes for shorter code and still easily identifies the property as an input or output.

+makeExample('style-guide/ts/05-12/app/heroes/shared/hero-button/hero-button.component.avoid.ts', 'example', 'app/heroes/shared/hero-button/hero-button.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/05-12/app/heroes/shared/hero-button/hero-button.component.ts', 'example', 'app/heroes/shared/hero-button/hero-button.component.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Avoid Renaming Inputs and Outputs
  <a id="05-13"></a>
  #### Style 05-13

.s-rule.avoid
  :marked
    **Avoid** renaming inputs and outputs, when possible.

.s-why.s-why-last
  :marked
    **Why?** May lead to confusion when the output or the input properties of a given directive are named a given way but exported differently as a public API.

+makeExample('style-guide/ts/05-13/app/heroes/shared/hero-button/hero-button.component.avoid.ts', 'example', 'app/heroes/shared/hero-button/hero-button.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/05-13/app/app.component.avoid.html', '', 'app/app.component.html')(avoid=1)
:marked

+makeTabs(
  `style-guide/ts/05-13/app/heroes/shared/hero-button/hero-button.component.ts,
  style-guide/ts/05-13/app/app.component.html`,
  'example,',
  `app/heroes/shared/hero-button/hero-button.component.ts,
  app/app.component.html`)
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Member Sequence
  <a id="05-14"></a>
  #### Style 05-14

.s-rule.do
  :marked
    **Do** place properties up top followed by methods.

.s-rule.do
  :marked
    **Do** place private members after public members, alphabetized.

.s-why.s-why-last
  :marked
    **Why?** Placing members in a consistent sequence makes it easy to read and helps we instantly identify which members of the component serve which purpose.

+makeExample('style-guide/ts/05-14/app/shared/toast/toast.component.avoid.ts', 'example', 'app/shared/toast/toast.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/05-14/app/shared/toast/toast.component.ts', 'example', 'app/shared/toast/toast.component.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Put Logic in Services
  <a id="05-15"></a>
  #### Style 05-15

.s-rule.do
  :marked
    **Do** limit logic in a component to only that required for the view. All other logic should be delegated to services.

.s-rule.do
  :marked
    **Do** move reusable logic to services and keep components simple and focused on their intended purpose.

.s-why
  :marked
    **Why?** Logic may be reused by multiple components when placed within a service and exposed via a function.

.s-why
  :marked
    **Why?** Logic in a service can more easily be isolated in a unit test, while the calling logic in the component can be easily mocked.

.s-why
  :marked
    **Why?** Removes dependencies and hides implementation details from the component.

.s-why.s-why-last
  :marked
    **Why?** Keeps the component slim, trim, and focused.

+makeExample('style-guide/ts/05-15/app/heroes/hero-list/hero-list.component.avoid.ts', '', 'app/heroes/hero-list/hero-list.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/05-15/app/heroes/hero-list/hero-list.component.ts', 'example', 'app/heroes/hero-list/hero-list.component.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Don't Prefix Output Properties
  <a id="05-16"></a>
  #### Style 05-16

.s-rule.do
  :marked
    **Do** name events without the prefix `on`.

.s-rule.do
  :marked
    **Do** name our event handler methods with the prefix `on` followed by the event name.

.s-why
  :marked
    **Why?** This is consistent with built-in events such as button clicks.

.s-why.s-why-last
  :marked
    **Why?** Angular allows for an [alternative syntax](https://angular.io/docs/ts/latest/guide/template-syntax.html#!#binding-syntax) `on-*`. If the event itself was prefixed with `on` this would result in an `on-onEvent` binding expression.

+makeExample('style-guide/ts/05-16/app/heroes/hero.component.avoid.ts', 'example', 'app/heroes/hero.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/05-16/app/app.component.avoid.html', '', 'app/app.component.html')(avoid=1)
:marked

+makeTabs(
  `style-guide/ts/05-16/app/heroes/hero.component.ts,
  style-guide/ts/05-16/app/app.component.html`,
  'example,',
  `app/heroes/hero.component.ts,
  app/app.component.html`)
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Put Presentation Logic in the Component Class
  <a id="05-17"></a>
  #### Style 05-17

.s-rule.do
  :marked
    **Do** put presentation logic in the Component class, and not in the template.

.s-why
  :marked
    **Why?** Logic will be contained in one place (the Component class) instead of being spread in two places.

.s-why.s-why-last
  :marked
    **Why?** Keeping the component's presentation logic in the class instead of the template improves testability, maintainability, and reusability.

+makeExample('style-guide/ts/05-17/app/heroes/hero-list/hero-list.component.avoid.ts', 'example', 'app/heroes/hero-list/hero-list.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/05-17/app/heroes/hero-list/hero-list.component.ts', 'example', 'app/heroes/hero-list/hero-list.component.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ## Directives

a(href="#toc") Back to top

.l-main-section
:marked
  ### Use Directives to Enhance an Existing Element
  <a id="06-01"></a>
  #### Style 06-01

.s-rule.do
  :marked
    **Do** use attribute directives when you have presentation logic without a template.

.s-why
  :marked
    **Why?** Attributes directives don't have an associated template.

.s-why.s-why-last
  :marked
    **Why?** An element may have more than one attribute directive applied.

+makeExample('style-guide/ts/06-01/app/shared/highlight.directive.ts', 'example', 'app/shared/highlight.directive.ts')
:marked

+makeExample('style-guide/ts/06-01/app/app.component.html', null, 'app/app.component.html')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Use HostListener and HostBinding Class Decorators
  <a id="06-03"></a>
  #### Style 06-03

.s-rule.do
  :marked
    **Do** use @HostListener and @HostBinding instead of the host property of the @Directive and @Component decorators:

.s-why
  :marked
    **Why?** The property or method name associated with @HostBinding or respectively @HostListener should be modified only in a single place - in the directive's class. In contrast if we use host we need to modify both the property declaration inside the controller, and the metadata associated to the directive.

.s-why.s-why-last
  :marked
    **Why?** The metadata declaration attached to the directive is shorter and thus more readable.

+makeExample('style-guide/ts/06-03/app/shared/validate.directive.avoid.ts', 'example', 'app/shared/validate.directive.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/06-03/app/shared/validate.directive.ts', 'example', 'app/shared/validate.directive.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ## Services

  ### Services are Singletons in Same Injector
  <a id="07-01"></a>
  #### Style 07-01

.s-rule.do
  :marked
    **Do** use services as singletons within the same injector. Use them for sharing data and functionality.

.s-why
  :marked
    **Why?** Services are ideal for sharing methods across a feature area or an app.

.s-why.s-why-last
  :marked
    **Why?** Services are ideal for sharing stateful in-memory data.

+makeExample('style-guide/ts/07-01/app/heroes/shared/hero.service.ts', 'example', 'app/heroes/shared/hero.service.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Single Responsibility
  <a id="07-02"></a>
  #### Style 07-02

.s-rule.do
  :marked
    **Do** create services with a single responsibility that is encapsulated by its context.

.s-rule.do
  :marked
    **Do** create a new service once the service begins to exceed that singular purpose.

.s-why
  :marked
    **Why?** When a service has multiple responsibilities, it becomes difficult to test.

.s-why.s-why-last
  :marked
    **Why?** When a service has multiple responsibilities, every Component or Service that injects it now carries the weight of them all.

a(href="#toc") Back to top

.l-main-section
:marked
  ### Providing a Service
  <a id="07-03"></a>
  #### Style 07-03

.s-rule.do
  :marked
    **Do** provide services to the Angular 2 injector at the top-most component where they will be shared.

.s-why
  :marked
    **Why?** The Angular 2 injector is hierarchical.

.s-why
  :marked
    **Why?** When providing the service to a top level component, that instance is shared and available to all child components of that top level component.

.s-why
  :marked
    **Why?** This is ideal when a service is sharing methods or state.

.s-why.s-why-last
  :marked
    **Why?** This is not ideal when two different components need different instances of a service. In this scenario it would be better to provide the service at the component level that needs the new and separate instance.

+makeTabs(
  `style-guide/ts/07-03/app/app.component.ts,
  style-guide/ts/07-03/app/heroes/hero-list/hero-list.component.ts`,
  '',
  `app/app.component.ts,
  app/heroes/hero-list/hero-list.component.ts`)
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ### Use the @Injectable() Class Decorator
  <a id="07-04"></a>
  #### Style 07-04

.s-rule.do
  :marked
    **Do** use the `@Injectable` class decorator instead of the `@Inject` parameter decorator when using types as tokens for the dependencies of a service.

.s-why
  :marked
    **Why?** The Angular DI mechanism resolves all the dependencies of our services based on their types declared with the services' constructors.

.s-why.s-why-last
  :marked
    **Why?** When a service accepts only dependencies associated with type tokens, the `@Injectable()` syntax is much less verbose compared to using `@Inject()` on each individual constructor parameter.

+makeExample('style-guide/ts/07-04/app/heroes/shared/hero-arena.service.avoid.ts', 'example', 'app/heroes/shared/hero-arena.service.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/07-04/app/heroes/shared/hero-arena.service.ts', 'example', 'app/heroes/shared/hero-arena.service.ts')
:marked

a(href="#toc") Back to top

.l-main-section
:marked
  ## Data Services

  ### Separate Data Calls
  <a id="08-01"></a>
  #### Style 08-01

.s-rule.do
  :marked
    **Do** refactor logic for making data operations and interacting with data to a service.

.s-rule.do
  :marked
    **Do** make data services responsible for XHR calls, local storage, stashing in memory, or any other data operations.

.s-why
  :marked
    **Why?** The component's responsibility is for the presentation and gathering of information for the view. It should not care how it gets the data, just that it knows who to ask for it. Separating the data services moves the logic on how to get it to the data service, and lets the component be simpler and more focused on the view.

.s-why
  :marked
    **Why?** This makes it easier to test (mock or real) the data calls when testing a component that uses a data service.

.s-why.s-why-last
  :marked
    **Why?** Data service implementation may have very specific code to handle the data repository. This may include headers, how to talk to the data, or other services such as `Http`. Separating the logic into a data service encapsulates this logic in a single place hiding the implementation from the outside consumers (perhaps a component), also making it easier to change the implementation.

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.l-main-section
:marked
  ## Lifecycle Hooks

  Use Lifecycle Hooks to tap into important events exposed by Angular.

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.l-main-section
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  ### Implement Lifecycle Hooks Interfaces
  <a id="09-01"></a>
  #### Style 09-01

.s-rule.do
  :marked
    **Do** implement the lifecycle hook interfaces.

.s-why.s-why-last
  :marked
    **Why?** We avoid unintentionally not calling the hook if we misspell the method.

+makeExample('style-guide/ts/09-01/app/heroes/shared/hero-button/hero-button.component.avoid.ts', 'example', 'app/heroes/shared/hero-button/hero-button.component.ts')(avoid=1)
:marked

+makeExample('style-guide/ts/09-01/app/heroes/shared/hero-button/hero-button.component.ts', 'example', 'app/heroes/shared/hero-button/hero-button.component.ts')
:marked

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.l-main-section
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  ## Routing

  Client-side routing is important for creating a navigation flow between a component tree hierarchy, and composing components that are made of many other child components.

a(href="#toc") Back to top

.l-main-section
:marked
  ### Component Router
  <a id="10-01"></a>
  #### Style 10-01

.s-rule.do
  :marked
    **Do** separate route configuration into a routing component file, also known as a component router.

.s-rule.do
  :marked
    **Do** use a `<router-outlet>` in the component router, where the routes will have their component targets display their templates.

.s-rule.do
  :marked
    **Do** focus the logic in the component router to the routing aspects and its target components.

.s-rule.do
  :marked
    **Do** extract other logic to services and other components.

.s-why
  :marked
    **Why?** A component that handles routing is known as the component router, thus this follows the Angular 2 routing pattern.

.s-why
  :marked
    **Why?** A component that handles routing is known as the componenter router.

.s-why.s-why-last
  :marked
    **Why?** The `<router-outlet>` indicates where the template should be displayed for the target route.

+makeExample('style-guide/ts/10-01/app/app.component.ts', '', 'app/app.component.ts')
:marked

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.l-main-section
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  ## Appendix

  Useful tools and tips for Angular 2.

a(href="#toc") Back to top

.l-main-section
:marked
  ### Codelyzer
  <a id="A-01"></a>
  #### Style A-01

.s-rule.do
  :marked
    **Do** use [codelyzer](https://www.npmjs.com/package/codelyzer) to follow this guide.

.s-rule.consider
  :marked
    **Consider** adjusting the rules in codelyzer to suit your needs.

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.l-main-section
:marked
  ### File Templates and Snippets
  <a id="A-02"></a>
  #### Style A-02

.s-rule.do
  :marked
    **Do** use file templates or snippets to help follow consistent styles and patterns. Here are templates and/or snippets for some of the web development editors and IDEs.

.s-rule.consider
  :marked
    **Consider** using [snippets](https://marketplace.visualstudio.com/items?itemName=johnpapa.Angular2) for [Visual Studio Code](https://code.visualstudio.com/) that follow these styles and guidelines.

:marked
  [![Use Extension](https://github.com/johnpapa/vscode-angular2-snippets/raw/master/images/use-extension.gif)](https://marketplace.visualstudio.com/items?itemName=johnpapa.Angular2)

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