angular-cn/aio/content/guide/reactive-forms.md

Reactive Forms

响应式表单

Reactive forms is an Angular technique for creating forms in a reactive style. This guide explains reactive forms as you follow the steps to build a "Hero Detail Editor" form.

响应式表单是 Angular 中用响应式风格创建表单的技术。 本章会在构建“英雄详情编辑器”的过程中，逐步讲解响应式表单的概念。

{@a toc}

Try the Reactive Forms live-example.

试试响应式表单的在线例子。

You can also run the Reactive Forms Demo version and choose one of the intermediate steps from the "demo picker" at the top.

你还可以运行响应式表单的演示程序，并从顶部选取一个中间步骤。

{@a intro}

Introduction to Reactive Forms

响应式表单简介

Angular offers two form-building technologies: reactive forms and template-driven forms. The two technologies belong to the @angular/forms library and share a common set of form control classes.

Angular 提供了两种构建表单的技术：响应式表单和模板驱动表单。 这两项技术都属于 @angular/forms 库，并且共享一组公共的表单控件类。

But they diverge markedly in philosophy, programming style, and technique. They even have their own modules: the ReactiveFormsModule and the FormsModule.

但是它们在设计哲学、编程风格和具体技术上有显著区别。 所以，它们都有自己的模块：ReactiveFormsModule 和 FormsModule。

Reactive forms

响应式表单

Angular reactive forms facilitate a reactive style of programming that favors explicit management of the data flowing between a non-UI data model (typically retrieved from a server) and a UI-oriented form model that retains the states and values of the HTML controls on screen. Reactive forms offer the ease of using reactive patterns, testing, and validation.

Angular 的响应式表单能让实现响应式编程风格更容易，这种编程风格更倾向于在非 UI 的数据模型（通常接收自服务器）之间显式的管理数据流， 并且用一个 UI 导向的表单模型来保存屏幕上 HTML 控件的状态和值。 响应式表单可以让使用响应式编程模式、测试和校验变得更容易。

With reactive forms, you create a tree of Angular form control objects in the component class and bind them to native form control elements in the component template, using techniques described in this guide.

使用响应式表单，你可以在组件中创建表单控件的对象树，并使用本章中传授的技巧把它们绑定到组件模板中的原生表单控件元素上。

You create and manipulate form control objects directly in the component class. As the component class has immediate access to both the data model and the form control structure, you can push data model values into the form controls and pull user-changed values back out. The component can observe changes in form control state and react to those changes.

你可以在组件类中直接创建和维护表单控件对象。由于组件类可以同时访问数据模型和表单控件结构， 因此你可以把表单模型值的变化推送到表单控件中，并把变化后的值拉取回来。 组件可以监听表单控件状态的变化，并对此做出响应。

One advantage of working with form control objects directly is that value and validity updates are always synchronous and under your control. You won't encounter the timing issues that sometimes plague a template-driven form and reactive forms can be easier to unit test.

直接使用表单控件对象的优点之一是值和有效性状态的更新总是同步的，并且在你的控制之下。 你不会遇到时序问题，这个问题有时在模板驱动表单中会成为灾难。而且响应式表单更容易进行单元测试。

In keeping with the reactive paradigm, the component preserves the immutability of the data model, treating it as a pure source of original values. Rather than update the data model directly, the component extracts user changes and forwards them to an external component or service, which does something with them (such as saving them) and returns a new data model to the component that reflects the updated model state.

在响应式编程范式中，组件会负责维护数据模型的不可变性，把模型当做纯粹的原始数据源。 组件不会直接更新数据模型，而是把用户的修改提取出来，把它们转发给外部的组件或服务，外部程序才会使用这些进行处理（比如保存它们）， 并且给组件返回一个新的数据模型，以反映模型状态的变化。

Using reactive form directives does not require you to follow all reactive priniciples, but it does facilitate the reactive programming approach should you choose to use it.

使用响应式表单的指令，并不要求你遵循所有的响应式编程原则，但它能让你更容易使用响应式编程方法，从而更愿意使用它。

Template-driven forms

模板驱动表单

Template-driven forms, introduced in the Template guide, take a completely different approach.

在模板一章中介绍过的模板驱动表单，是一种完全不同的方式。

You place HTML form controls (such as <input> and <select>) in the component template and bind them to data model properties in the component, using directives like ngModel.

你把 HTML 表单控件（比如 <input> 和 <select>）放进组件模板中，并用 ngModel 等指令把它们绑定到组件中数据模型的属性上。

You don't create Angular form control objects. Angular directives create them for you, using the information in your data bindings. You don't push and pull data values. Angular handles that for you with ngModel. Angular updates the mutable data model with user changes as they happen.

你不用自己创建 Angular 表单控件对象。Angular 指令会使用数据绑定中的信息创建它们。 你不用自己推送和拉取数据。Angular 使用 ngModel 来替你管理它们。 当用户做出修改时，Angular 会据此更新可变的数据模型。

For this reason, the ngModel directive is not part of the ReactiveFormsModule.

因此，ngModel 并不是 ReactiveFormsModule 模块的一部分。

While this means less code in the component class, template-driven forms are asynchronous which may complicate development in more advanced scenarios.

虽然这意味着组件中的代码更少，但是模板驱动表单是异步工作的，这可能在更高级的场景中让开发复杂化。

{@a async-vs-sync}

Async vs. sync

异步 vs. 同步

Reactive forms are synchronous. Template-driven forms are asynchronous. It's a difference that matters.

响应式表单是同步的。模板驱动表单是异步的。这个不同点很重要。

In reactive forms, you create the entire form control tree in code. You can immediately update a value or drill down through the descendents of the parent form because all controls are always available.

使用响应式表单，你会在代码中创建整个表单控件树。 你可以立即更新一个值或者深入到表单中的任意节点，因为所有的控件都始终是可用的。

Template-driven forms delegate creation of their form controls to directives. To avoid "changed after checked" errors, these directives take more than one cycle to build the entire control tree. That means you must wait a tick before manipulating any of the controls from within the component class.

模板驱动表单会委托指令来创建它们的表单控件。 为了消除“检查完后又变化了”的错误，这些指令需要消耗一个以上的变更检测周期来构建整个控件树。 这意味着在从组件类中操纵任何控件之前，你都必须先等待一个节拍。

For example, if you inject the form control with a @ViewChild(NgForm) query and examine it in the ngAfterViewInit lifecycle hook, you'll discover that it has no children. You must wait a tick, using setTimeout, before you can extract a value from a control, test its validity, or set it to a new value.

比如，如果你用 @ViewChild(NgForm) 查询来注入表单控件，并在生命周期钩子 ngAfterViewInit中检查它，就会发现它没有子控件。 你必须使用 setTimeout 等待一个节拍才能从控件中提取值、测试有效性，或把它设置为新值。

The asynchrony of template-driven forms also complicates unit testing. You must wrap your test block in async() or fakeAsync() to avoid looking for values in the form that aren't there yet. With reactive forms, everything is available when you expect it to be.

模板驱动表单的异步性让单元测试也变得复杂化了。 你必须把测试代码包裹在 async() 或 fakeAsync() 中来解决要查阅的值尚不存在的情况。 使用响应式表单，在所期望的时机一切都是可用的。

Which is better, reactive or template-driven?

哪一个更好？响应式还是模板驱动？

Neither is "better". They're two different architectural paradigms, with their own strengths and weaknesses. Choose the approach that works best for you. You may decide to use both in the same application.

没有哪个“更好”。 它们是两种架构范式，各有优缺点。 请自行选择更合适的方法，甚至可以在同一个应用中同时使用它们。

The balance of this reactive forms guide explores the reactive paradigm and concentrates exclusively on reactive forms techniques. For information on template-driven forms, see the Forms guide.

在这章响应式表单中，只专注于响应式范式以及响应式表单技术的详情。 要了解关于模板驱动表单的更多信息，参见表单一章。

In the next section, you'll set up your project for the reactive form demo. Then you'll learn about the Angular form classes and how to use them in a reactive form.

在下一节，你要先准备一个响应式表单范例的项目，然后就可以开始学习Angular 表单类，并在响应式表单中使用它们了。

{@a setup}

Setup

准备工作

Create a new project named angular-reactive-forms:

创建一个名叫angular-reactive-forms的新项目：

ng new angular-reactive-forms

{@a data-model}

Create a data model

创建数据模型

The focus of this guide is a reactive forms component that edits a hero. You'll need a hero class and some hero data.

本章的焦点是响应式表单组件以及编辑一个英雄。 你需要一个 Hero 类和一些英雄数据。

Using the CLI, generate a new class named data-model:

使用 CLI 创建一个名叫 data-model 的新类：

ng generate class data-model

And copy the content below:

并复制下列内容：

The file exports two classes and two constants. The Address and Hero classes define the application data model. The heroes and states constants supply the test data.

这个文件导出两个类和两个常量。Address 和 Hero 类定义应用的数据模型。 heroes 和 states 常量提供测试数据。

{@a create-component}

Create a reactive forms component

创建响应式表单组件

Generate a new component named HeroDetail:

生成一个名叫 HeroDetail 的新组件：

ng generate component HeroDetail

And import:

并导入：

Next, update the HeroDetailComponent class with a FormControl. FormControl is a directive that allows you to create and manage a FormControl instance directly.

接下来，创建并导出一个带 FormControl 的 HeroDetailComponent 类。 FormControl 是一个指令，它允许你直接创建并管理一个 FormControl 实例。

Here you are creating a FormControl called name. It will be bound in the template to an HTML input box for the hero name.

这里你创建了一个名叫 name 的 FormControl。 它将会绑定到模板中的一个 input 框，表示英雄的名字。

A FormControl constructor accepts three, optional arguments: the initial data value, an array of validators, and an array of async validators.

FormControl 构造函数接收三个可选参数： 初始值、验证器数组和异步验证器数组。

This simple control doesn't have data or validators. In real apps, most form controls have both.

最简单的控件并不需要数据或验证器，但是在实际应用中，大部分表单控件都会同时具备它们。

This guide touches only briefly on Validators. For an in-depth look at them, read the Form Validation guide.

本章中只会接触 Validators 中的一点点，要想更深入的了解它们，请阅读表单验证一章。

{@a create-template}

Create the template

创建模板

Now update the component's template, with the following markup.

现在，修改组件的模板文件 src/app/hero-detail.component.html，内容如下：

To let Angular know that this is the input that you want to associate to the name FormControl in the class, you need [formControl]="name" in the template on the <input>.

要让 Angular 知道你希望把这个输入框关联到类中的 FormControl 型属性 name，就要在模板中的 <input> 上加一句 [formControl]="name"。

Disregard the form-control CSS class. It belongs to the Bootstrap CSS library, not Angular. It styles the form but in no way impacts the logic of the form.

请忽略 CSS 类 form-control，它属于Bootstrap CSS library而不是 Angular。 它会为表单添加样式，但是对表单的逻辑毫无影响。

{@a import}

Import the ReactiveFormsModule

导入 ReactiveFormsModule

The HeroDetailComponent template uses formControlName directive from the ReactiveFormsModule.

HeroDetailComponent 的模板中使用了来自 ReactiveFormsModule 的 formControlName。

Do the following two things in app.module.ts:

在 app.module.ts 中做了下面两件事：

1. Use a JavaScript import statement to access the ReactiveFormsModule.

   使用 JavaScript 的 import 语句访问 ReactiveFormsModule 和 HeroDetailComponent。

2. Add ReactiveFormsModule to the AppModule's imports list.

   把 ReactiveFormsModule 添加到 AppModule 的 imports 列表中。

{@a update}

Display the HeroDetailComponent

显示 HeroDetailComponent

Revise the AppComponent template so it displays the HeroDetailComponent.

修改 AppComponent 的模板，以便显示 HeroDetailComponent。

{@a essentials}

Essential form classes

基础的表单类

It may be helpful to read a brief description of the core form classes.

阅读一下这些核心表单类的简短描述也许会有用。

• AbstractControl is the abstract base class for the three concrete form control classes: FormControl, FormGroup, and FormArray. It provides their common behaviors and properties, some of which are observable.

  AbstractControl是三个具体表单类的抽象基类。 并为它们提供了一些共同的行为和属性，其中有些是可观察对象（Observable）。

• FormControl tracks the value and validity status of an individual form control. It corresponds to an HTML form control such as an input box or selector.

  FormControl 用于跟踪一个单独的表单控件的值和有效性状态。它对应于一个 HTML 表单控件，比如输入框和下拉框。

• FormGroup tracks the value and validity state of a group of AbstractControl instances. The group's properties include its child controls. The top-level form in your component is a FormGroup.

  FormGroup用于 跟踪一组AbstractControl 的实例的值和有效性状态。 该组的属性中包含了它的子控件。 组件中的顶级表单就是一个 FormGroup。

• FormArray tracks the value and validity state of a numerically indexed array of AbstractControl instances.

  FormArray用于跟踪 AbstractControl 实例组成的有序数组的值和有效性状态。

You'll learn more about these classes as you work through this guide.

随着本章的深入，你将学到关于这些类的更多知识。

Style the app

为应用添加样式

You used bootstrap CSS classes in the template HTML of both the AppComponent and the HeroDetailComponent. Add the bootstrap CSS stylesheet to the head of styles.css:

你在 AppComponent 和 HeroDetailComponent 的模板中使用 Bootstrap 中的 CSS 类。请把 bootstrap 的CSS 样式表文件添加到 index.html 的 head 区。

Now that everything is wired up, the browser should display something like this:

这些做好之后，浏览器中应该显示成这样：

{@a formgroup}

Add a FormGroup

添加 FormGroup

Usually, if you have multiple FormControls, you'll want to register them within a parent FormGroup. This is simple to do. To add a FormGroup, add it to the imports section of hero-detail.component.ts:

通常，如果有多个 FormControl，你会希望把它们注册进一个父 FormGroup 中。这很容易。只要把它加入 hero-detail.component.ts 的 import 区就可以了。

In the class, wrap the FormControl in a FormGroup called heroForm as follows:

在这个类中，把 FormControl 包裹进了一个名叫 heroForm 的 FormGroup 中，代码如下：

Now that you've made changes in the class, they need to be reflected in the template. Update hero-detail.component.html by replacing it with the following.

现在你改完了这个类，该把它映射到模板中了。把 hero-detail.component.html 改成这样：

Notice that now the single input is in a form element. The novalidate attribute in the <form> element prevents the browser from attempting native HTML validations.

注意，现在单行输入框位于一个 form 元素中。<form> 元素上的 novalidate 属性会阻止浏览器使用原生 HTML 中的表单验证器。

formGroup is a reactive form directive that takes an existing FormGroup instance and associates it with an HTML element. In this case, it associates the FormGroup you saved as heroForm with the form element.

formGroup 是一个响应式表单的指令，它拿到一个现有 FormGroup 实例，并把它关联到一个 HTML 元素上。 这种情况下，它关联到的是 form 元素上的 FormGroup 实例 heroForm。

Because the class now has a FormGroup, you must update the template syntax for associating the input with the corresponding FormControl in the component class. Without a parent FormGroup, [formControl]="name" worked earlier because that directive can stand alone, that is, it works without being in a FormGroup. With a parent FormGroup, the name input needs the syntax formControlName=name in order to be associated with the correct FormControl in the class. This syntax tells Angular to look for the parent FormGroup, in this case heroForm, and then inside that group to look for a FormControl called name.

由于现在有了一个 FormGroup，因此你必须修改模板语法来把输入框关联到组件类中对应的 FormControl 上。 以前没有父 FormGroup 的时候，[formControl]="name" 也能正常工作，因为该指令可以独立工作，也就是说，不在 FormGroup 中时它也能用。 有了 FormGroup，name 输入框就需要再添加一个语法 formControlName=name，以便让它关联到类中正确的 FormControl 上。 这个语法告诉 Angular，查阅父 FormGroup（这里是 heroForm），然后在这个 FormGroup 中查阅一个名叫 name 的 FormControl。

Disregard the form-group CSS class. It belongs to the Bootstrap CSS library, not Angular. Like the form-control class, it styles the form but in no way impacts its logic.

请无视 CSS 类 form-group，它属于Bootstrap CSS library而不是 Angular。 就像 form-control 类一样，它只是为表单添加样式，而对表单逻辑毫无影响。

The form looks great. But does it work? When the user enters a name, where does the value go?

表单看起来很棒，但是它能用吗？ 当用户输入名字时，它的值去了哪里？

{@a json}

Taking a look at the form model

表单模型概览

The value goes into the form model that backs the group's FormControls. To see the form model, add the following line after the closing form tag in the hero-detail.component.html:

这个值进入了幕后表单模型中的 FormControl 构成的表单组。 要想知道表单模型是什么样的，请在 hero-detail.component.html 的 form 标签紧后面添加如下代码：

The heroForm.value returns the form model. Piping it through the JsonPipe renders the model as JSON in the browser:

heroForm.value 会返回表单模型。 用 JsonPipe 管道把这个模型以 JSON 格式渲染到浏览器中。

The initial name property value is the empty string. Type into the name input box and watch the keystokes appear in the JSON.

最初的 name 属性是个空字符串，在 name 输入框中输入之后，可以看到这些按键出现在了 JSON 中。

Great! You have the basics of a form.

真棒！你有了一个基本版表单。

In real life apps, forms get big fast. FormBuilder makes form development and maintenance easier.

在真实的应用中，表单很快就会变大。 FormBuilder 能让表单开发和维护变得更简单。

{@a formbuilder}

Introduction to FormBuilder

FormBuilder 简介

The FormBuilder class helps reduce repetition and clutter by handling details of control creation for you.

FormBuilder 类能通过处理控件创建的细节问题来帮你减少重复劳动。

To use FormBuilder, you need to import it into hero-detail.component.ts:

要使用 FormBuilder，你就要先把它导入到 hero-detail.component.ts 中：

Use it now to refactor the HeroDetailComponent into something that's a little easier to read and write, by following this plan:

现在，你要遵循下列步骤用 FormBuilder 来把 HeroDetailComponent 重构得更加容易读写。

• Explicitly declare the type of the heroForm property to be FormGroup; you'll initialize it later.

  明确把 heroForm 属性的类型声明为 FormGroup，稍后你会初始化它。

• Inject a FormBuilder into the constructor.

  把 FormBuilder 注入到构造函数中。

• Add a new method that uses the FormBuilder to define the heroForm; call it createForm.

  添加一个名叫 createForm 的新方法，它会用 FormBuilder 来定义 heroForm。

• Call createForm in the constructor.

  在构造函数中调用 createForm。

The revised HeroDetailComponent looks like this:

修改过的 HeroDetailComponent 代码如下：

FormBuilder.group is a factory method that creates a FormGroup.   FormBuilder.group takes an object whose keys and values are FormControl names and their definitions. In this example, the name control is defined by its initial data value, an empty string.

FormBuilder.group 是一个用来创建 FormGroup 的工厂方法，它接受一个对象，对象的键和值分别是 FormControl 的名字和它的定义。 在这个例子中，name 控件的初始值是空字符串。

Defining a group of controls in a single object makes for a compact, readable style. It beats writing an equivalent series of new FormControl(...) statements.

把一组控件定义在一个单一对象中，可以更加紧凑、易读。 完成相同功能时，这种形式优于一系列 new FormControl(...) 语句。

{@a validators}

Validators.required

Validators.required 验证器

Though this guide doesn't go deeply into validations, here is one example that demonstrates the simplicity of using Validators.required in reactive forms.

虽然本章不会深入讲解验证机制，但还是有一个例子来示范如何简单的在响应式表单中使用 Validators.required。

First, import the Validators symbol.

首先，导入 Validators 符号。

To make the name FormControl required, replace the name property in the FormGroup with an array. The first item is the initial value for name; the second is the required validator, Validators.required.

要想让 name 这个 FormControl 是必须的，请把 FormGroup 中的 name 属性改为一个数组。第一个条目是 name 的初始值，第二个是 required 验证器：Validators.required。

Reactive validators are simple, composable functions. Configuring validation is harder in template-driven forms where you must wrap validators in a directive.

响应式验证器是一些简单、可组合的函数。 在模板驱动表单中配置验证器有些困难，因为你必须把验证器包装进指令中。

Update the diagnostic message at the bottom of the template to display the form's validity status.

修改模板底部的诊断信息，以显示表单的有效性状态。

The browser displays the following:

浏览器会显示下列内容：

Validators.required is working. The status is INVALID because the input box has no value. Type into the input box to see the status change from INVALID to VALID.

Validators.required 生效了，但状态还是 INVALID，因为输入框中还没有值。 在输入框中输入，就会看到这个状态从 INVALID 变成了 VALID。

In a real app, you'd replace the diagnosic message with a user-friendly experience.

在真实的应用中，你要把这些诊断信息替换成用户友好的信息。

Using Validators.required is optional for the rest of the guide. It remains in each of the following examples with the same configuration.

在本章的其余部分，Validators.required 是可有可无的，但在每个与此范例配置相同的范例中都会保留它。

For more on validating Angular forms, see the Form Validation guide.

要了解 Angular 表单验证器的更多知识，参见表单验证器一章。

More FormControls

更多的表单控件（FormControl）

A hero has more than a name. A hero has an address, a super power and sometimes a sidekick too.

每个英雄可以有多个名字，还有一个住址、一项超能力，有时还会有一个副手。

The address has a state property. The user will select a state with a <select> box and you'll populate the <option> elements with states. So import states from data-model.ts.

住址中有一个所在州属性，用户将会从 <select> 框中选择一个州，你会用 <option> 元素渲染各个州。从 data-model.ts 中导入 states（州列表）。

Declare the states property and add some address FormControls to the heroForm as follows.

声明 states 属性并往 heroForm 中添加一些表示住址的 FormControl，代码如下：

Then add corresponding markup in hero-detail.component.html within the form element.

然后在 hero-detail.component.html 文件中把对应的脚本添加到 form 元素中。

Reminder: Ignore the many mentions of form-group, form-control, center-block, and checkbox in this markup. Those are bootstrap CSS classes that Angular itself ignores. Pay attention to the [formGroup] and formControlName attributes. They are the Angular directives that bind the HTML controls to the Angular FormGroup and FormControl properties in the component class.

注意：不用管这些脚本中提到的 form-group、form-control、center-block 和 checkbox 等。 它们是来自 Bootstrap 的 CSS 类，Angular 本身不会管它们。 注意 formGroupName 和 formControlName 属性。 他们是 Angular 指令，用于把相应的 HTML 控件绑定到组件中的 FormGroup 和 FormControl 类型的属性上。

The revised template includes more text inputs, a select box for the state, radio buttons for the power, and a checkbox for the sidekick.

修改过的模板包含更多文本输入框，一个 state 选择框，power（超能力）的单选按钮和一个 sidekick 检查框。

You must bind the option's value property with [value]="state". If you do not bind the value, the select shows the first option from the data model.

你要用 [value]="state" 来绑定选项的 value 属性。 如果不绑定这个值，这个选择框就会显示来自数据模型中的第一个选项。

The component class defines control properties without regard for their representation in the template. You define the state, power, and sidekick controls the same way you defined the name control. You tie these controls to the template HTML elements in the same way, specifying the FormControl name with the formControlName directive.

组件类定义了控件属性而不用管它们在模板中的表现形式。 你可以像定义 name 控件一样定义 state、power 和 sidekick 控件，并用 formControlName 指令来指定 FormControl 的名字。

See the API reference for more information about radio buttons, selects, and checkboxes.

参见 API 参考手册中的radio buttons、 selects和 checkboxes

{@a grouping}

Nested FormGroups

多级 FormGroup

This form is getting big and unwieldy. You can group some of the related FormControls into a nested FormGroup. The street, city, state, and zip are properties that would make a good address FormGroup. Nesting groups and controls in this way allows you to mirror the hierarchical structure of the data model and helps track validation and state for related sets of controls.

这个表单变得越来越大、越来越笨重。 你可以把一些相关的 FormControl 组织到多级 FormGroup 中。 street、city、state 和 zip 属性就可以作为一个名叫 address 的 FormGroup。 用这种方式，多级表单组和控件可以让你轻松地映射多层结构的数据模型，以帮你跟踪这组相关控件的有效性和状态。

You used the FormBuilder to create one FormGroup in this component called heroForm. Let that be the parent FormGroup. Use FormBuilder again to create a child FormGroup that encapsulates the address controls; assign the result to a new address property of the parent FormGroup.

你用 FormBuilder 在这个名叫 heroForm 的组件中创建一个 FormGroup，并把它用作父 FormGroup。 再次使用 FormBuilder 创建一个子级 FormGroup，其中包括这些住址控件。把结果赋值给父 FormGroup 中新的 address 属性。

You’ve changed the structure of the form controls in the component class; you must make corresponding adjustments to the component template.

你已经修改了组件类中表单控件的结构，还必须对组件模板进行相应的调整。

In hero-detail.component.html, wrap the address-related FormControls in a div. Add a formGroupName directive to the div and bind it to "address". That's the property of the address child FormGroup within the parent FormGroup called heroForm.

在 hero-detail.component.html 中，把与住址有关的 FormControl 包裹进一个 div 中。 往这个 div 上添加一个 formGroupName 指令，并且把它绑定到 "address" 上。 这个 address 属性是一个 FormGroup，它的父 FormGroup 就是 heroForm。

To make this change visually obvious, slip in an <h4> header near the top with the text, Secret Lair. The new address HTML looks like this:

要让这个变化更加明显，在文本的顶部加入一个 <h4> 头：Secret Lair。 新的住址组的 HTML 如下：

After these changes, the JSON output in the browser shows the revised form model with the nested address FormGroup:

做完这些之后，浏览器中的 JSON 输出就变成了带有多级 FormGroup 的住址。

Great! You’ve made a group and you can see that the template and the form model are talking to one another.

真棒！你制作了一个控件组，并且可以看到模板和表单模型已经能彼此通讯了。

{@a properties}

Inspect FormControl Properties

查看 FormControl 的属性

At the moment, you're dumping the entire form model onto the page. Sometimes you're interested only in the state of one particular FormControl.

此刻，你把整个表单模型展示在了页面里。 但有时你可能只关心一个特定 FormControl 的状态。

You can inspect an individual FormControl within a form by extracting it with the .get() method. You can do this within the component class or display it on the page by adding the following to the template, immediately after the {{form.value | json}} interpolation as follows:

你可以使用 .get() 方法来提取表单中一个单独 FormControl 的状态。 你可以在组件类中这么做，或者通过往模板中添加下列代码来把它显示在页面中，就添加在 {{form.value | json}} 插值表达式的紧后面：

To get the state of a FormControl that’s inside a FormGroup, use dot notation to path to the control.

要点取得 FormGroup 中的 FormControl 的状态，使用点语法来指定到控件的路径。

You can use this technique to display any property of a FormControl such as one of the following:

你可以使用此技术来显示 FromControl 的任意属性，代码如下：

<th>

  Property

  属性

</th>

<th>

  Description

  说明

</th>

<td>

  <code>myControl.value</code>

</td>

<td>

  the value of a `FormControl`.

  `FormControl` 的值。

</td>

<td>

  <code>myControl.status</code>

</td>

<td>

  the validity of a `FormControl`. Possible values: `VALID`,
   `INVALID`, `PENDING`, or `DISABLED`.

  `FormControl` 的有效性。可能的值有 `VALID`、`INVALID`、`PENDING` 或 `DISABLED`。

</td>

<td>

  <code>myControl.pristine</code>

</td>

<td>

  `true` if the user has _not_ changed the value in the UI.
  Its opposite is `myControl.dirty`.

  如果用户*尚未*改变过这个控件的值，则为 `true`。它总是与 `myControl.dirty` 相反。

</td>

<td>

  <code>myControl.untouched</code>

</td>

<td>

  `true` if the control user has not yet entered the HTML control
   and triggered its blur event. Its opposite is `myControl.touched`.

  如果用户尚未进入这个 HTML 控件，也没有触发过它的 `blur`（失去焦点）事件，则为 `true`。
  它是 `myControl.touched` 的反义词。

</td>

Learn about other FormControl properties in the AbstractControl API reference.

要了解 FormControl 的更多属性，参见 API 参考手册的AbstractControl部分。

One common reason for inspecting FormControl properties is to make sure the user entered valid values. Read more about validating Angular forms in the Form Validation guide.

检查 FormControl 属性的另一个原因是确保用户输入了有效的值。 要了解更多关于 Angular 表单验证的知识，参见表单验证一章。

{@a data-model-form-model}

The data model and the form model

数据模型与表单模型

At the moment, the form is displaying empty values. The HeroDetailComponent should display values of a hero, possibly a hero retrieved from a remote server.

此刻，表单显示的是空值。 HeroDetailComponent 应该显示一个英雄的值，这个值可能接收自远端服务器。

In this app, the HeroDetailComponent gets its hero from a parent HeroListComponent

在这个应用中，HeroDetailComponent 从它的父组件 HeroListComponent 中取得一个英雄。

The hero from the server is the data model. The FormControl structure is the form model.

来自服务器的 hero 就是数据模型，而 FormControl 的结构就是表单模型。

The component must copy the hero values in the data model into the form model. There are two important implications:

组件必须把数据模型中的英雄值复制到表单模型中。这里隐含着两个非常重要的点。

1. The developer must understand how the properties of the data model map to the properties of the form model.

   开发人员必须理解数据模型是如何映射到表单模型中的属性的。

2. User changes flow from the DOM elements to the form model, not to the data model. The form controls never update the data model.

   用户修改时的数据流是从 DOM 元素流向表单模型的，而不是数据模型。表单控件永远不会修改数据模型。

The form and data model structures need not match exactly. You often present a subset of the data model on a particular screen. But it makes things easier if the shape of the form model is close to the shape of the data model.

表单模型和数据模型的结构并不需要精确匹配。在一个特定的屏幕上，你通常只会展现数据模型的一个子集。 但是表单模型的形态越接近数据模型，事情就会越简单。

In this HeroDetailComponent, the two models are quite close.

在 HeroDetailComponent 中，这两个模型是非常接近的。

Recall the definition of Hero in data-model.ts:

回忆一下 data-model.ts 中的 Hero 定义：

Here, again, is the component's FormGroup definition.

这里又是组件的 FormGroup 定义。

There are two significant differences between these models:

在这些模型中有两点显著的差异：

1. The Hero has an id. The form model does not because you generally don't show primary keys to users.

   Hero 有一个 id。表单模型中则没有，因为你通常不会把主键展示给用户。

2. The Hero has an array of addresses. This form model presents only one address, a choice revisited below.

   Hero 有一个住址数组。这个表单模型只表示了一个住址，稍后的修改则可以表示多个。

Nonetheless, the two models are pretty close in shape and you'll see in a moment how this alignment facilitates copying the data model properties to the form model with the patchValue and setValue methods.

虽然如此，这两个模型的形态仍然是非常接近的，你很快就会看到如何用 patchValue 和 setValue 方法来把数据模型拷贝到表单模型中。

Take a moment to refactor the address FormGroup definition for brevity and clarity as follows:

花一点时间来重构一下 address 这个 FormGroup 定义，来让它更简洁清晰，代码如下：

Also be sure to update the import from data-model so you can reference the Hero and Address classes:

为了确保从 data-model 中导入，你可以引用 Hero 和 Address 类：

{@a set-data}

Populate the form model with setValue and patchValue

使用 setValue 和 patchValue 来操纵表单模型

Previously you created a control and initialized its value at the same time. You can also initialize or reset the values later with the setValue and patchValue methods.

以前，你创建了控件，并同时初始化它的值。 你也可以稍后用 setValue 和 patchValue 来初始化或重置这些值。

setValue

setValue 方法

With setValue, you assign every form control value at once by passing in a data object whose properties exactly match the form model behind the FormGroup.

借助**setValue**，你可以立即设置每个表单控件的值，只要把与表单模型的属性精确匹配的数据模型传进去就可以了。

The setValue method checks the data object thoroughly before assigning any form control values.

setValue 方法会在赋值给任何表单控件之前先检查数据对象的值。

It will not accept a data object that doesn't match the FormGroup structure or is missing values for any control in the group. This way, it can return helpful error messages if you have a typo or if you've nested controls incorrectly. patchValue will fail silently.

它不会接受一个与 FormGroup 结构不同或缺少表单组中任何一个控件的数据对象。 这种方式下，如果你有什么拼写错误或控件嵌套的不正确，它就能返回一些有用的错误信息。 patchValue 会默默地失败。

On the other hand,setValue will catch the error and report it clearly.

而 setValue 会捕获错误，并清晰的报告它。

Notice that you can almost use the entire hero as the argument to setValue because its shape is similar to the component's FormGroup structure.

注意，你几乎可以把这个 hero 用作 setValue 的参数，因为它的形态与组件的 FormGroup 结构是非常像的。

You can only show the hero's first address and you must account for the possibility that the hero has no addresses at all. This explains the conditional setting of the address property in the data object argument:

你现在只能显示英雄的第一个住址，不过你还必须考虑 hero 完全没有住址的可能性。 下面的例子解释了如何在数据对象参数中对 address 属性进行有条件的设置：

patchValue

patchValue 方法

With patchValue, you can assign values to specific controls in a FormGroup by supplying an object of key/value pairs for just the controls of interest.

借助**patchValue**，你可以通过提供一个只包含要更新的控件的键值对象来把值赋给 FormGroup 中的指定控件。

This example sets only the form's name control.

这个例子只会设置表单的 name 控件。

With patchValue you have more flexibility to cope with wildly divergent data and form models. But unlike setValue, patchValue cannot check for missing control values and does not throw helpful errors.

借助**patchValue**，你可以更灵活地解决数据模型和表单模型之间的差异。 但是和 setValue 不同，patchValue 不会检查缺失的控件值，并且不会抛出有用的错误信息。

When to set form model values (ngOnChanges)

什么时候设置表单的模型值（ngOnChanges）

Now you know how to set the form model values. But when do you set them? The answer depends upon when the component gets the data model values.

现在，你已经知道了如何设置表单模型的值，但是什么时候设置它门呢？ 答案取决于组件何时得到数据模型的值。

The HeroDetailComponent in this reactive forms sample is nested within a master/detail HeroListComponent (discussed below). The HeroListComponent displays hero names to the user. When the user clicks on a hero, the list component passes the selected hero into the HeroDetailComponent by binding to its hero input property.

这个响应式表单范例中的 HeroDetailComponent 组件嵌套在一个主/从结构的 HeroListComponent（稍后讨论）中。 HeroListComponent 组件把英雄的名字显示给用户。 当用户点击一个英雄时，列表组件把所选的英雄通过输入属性 hero 传给 HeroDetailComponent。

In this approach, the value of hero in the HeroDetailComponent changes every time the user selects a new hero. You should call setValue in the ngOnChanges hook, which Angular calls whenever the input hero property changes as the following steps demonstrate.

这种方式下，每当用户选择一个新英雄时，HeroDetailComponent 中的 hero 值就会发生变化。 你可以在ngOnChanges钩子中调用 setValue，就像例子中所演示的那样， 每当输入属性 hero 发生变化时，Angular 就会调用它。

First, import the OnChanges and Input symbols in hero-detail.component.ts.

首先，在 hero-detail.component.ts 中导入 OnChanges 和 Input 符号。

Add the hero input property.

添加输入属性 hero。

Add the ngOnChanges method to the class as follows:

向该类中添加 ngOnChanges 方法，代码如下：

reset the form flags

重置表单的标识。

You should reset the form when the hero changes so that control values from the previous hero are cleared and status flags are restored to the pristine state. You could call reset at the top of ngOnChanges like this.

你应该在更换英雄的时候重置表单，以便来自前一个英雄的控件值被清除，并且其状态被恢复为 pristine（原始）状态。 你可以在 ngOnChanges 的顶部调用 reset，就像这样：

The reset method has an optional state value so you can reset the flags and the control values at the same time. Internally, reset passes the argument to setValue. A little refactoring and ngOnChanges becomes this:

reset 方法有一个可选的 state 值，让你能在重置状态的同时顺便设置控件的值。 在内部实现上，reset 会把该参数传给了 setValue。 略微重构之后，ngOnChanges 会变成这样：

{@a hero-list}

Create the HeroListComponent and HeroService

创建 HeroListComponent 和 HeroService

The HeroDetailComponent is a nested sub-component of the HeroListComponent in a master/detail view. Together they look a bit like this:

HeroDetalComponent 是一个嵌套在 HeroListComponent 的主从视图中的子组件。如果把它们放在一起就是这样的：

The HeroListComponent uses an injected HeroService to retrieve heroes from the server and then presents those heroes to the user as a series of buttons. The HeroService emulates an HTTP service. It returns an Observable of heroes that resolves after a short delay, both to simulate network latency and to indicate visually the necessarily asynchronous nature of the application.

HeroListComponent 使用一个注入进来的 HeroService 来从服务器获取英雄列表，然后用一系列按钮把这些英雄展示给用户。 HeroService 模拟了 HTTP 服务。 它返回一个英雄组成的 Observable 对象，并会在短暂的延迟之后被解析出来，这是为了模拟网络延迟，并展示应用在自然延迟下的异步效果。

When the user clicks on a hero, the component sets its selectedHero property which is bound to the hero input property of the HeroDetailComponent. The HeroDetailComponent detects the changed hero and re-sets its form with that hero's data values.

当用户点击一个英雄时，组件设置它的 selectedHero 属性，它绑定到 HeroDetailComponent 的输入属性 hero 上。 HeroDetailComponent 检测到英雄的变化，并使用当前英雄的值重置此表单。

A "Refresh" button clears the hero list and the current selected hero before refetching the heroes.

"刷新"按钮清除英雄列表和当前选中的英雄，然后重新获取英雄列表。

The remaining HeroListComponent and HeroService implementation details are not relevant to understanding reactive forms. The techniques involved are covered elsewhere in the documentation, including the Tour of Heroes here and here.

HeroListComponent 和 HeroService 的其余部分的实现细节与响应式表单无关。 那些技术涵盖于本文档中的其它部分，包括*《英雄指南》*中的这里和这里。

If you're coding along with the steps in this reactive forms tutorial, generate the pertinent files based on the source code displayed below. Notice that hero-list.component.ts imports Observable and finally while hero.service.ts imports Observable, of, and delay from rxjs. Then return here to learn about form array properties.

如果你正在随着本教程写代码，可以基于下面显示的代码来创建相应的文件。 注意，hero-list.component.ts 从 rxjs 中导入了 Observable 和 finally，而 hero.service.ts 导入了 Observable、of 和 delay。 然后回来继续学习表单数组的属性。

{@a form-array}

Use FormArray to present an array of FormGroups

使用 FormArray 来表示 FormGroup 数组

So far, you've seen FormControls and FormGroups. A FormGroup is a named object whose property values are FormControls and other FormGroups.

以前，我们见过了 FormControl 和 FormGroup。 FormGroup 是一个命名对象，它的属性值是 FormControl 和其它的 FormGroup。

Sometimes you need to present an arbitrary number of controls or groups. For example, a hero may have zero, one, or any number of addresses.

有时你需要表示任意数量的控件或控件组。 比如，一个英雄可能拥有 0、1 或任意数量的住址。

The Hero.addresses property is an array of Address instances. An address FormGroup can display one Address. An Angular FormArray can display an array of address FormGroups.

Hero.addresses 属性就是一个 Address 实例的数组。 一个住址的 FormGroup 可以显示一个 Address 对象。 而 FormArray 可以显示一个住址 FormGroup 的数组。

To get access to the FormArray class, import it into hero-detail.component.ts:

要访问 FormArray 类，请先把它导入 hero-detail.component.ts 中：

To work with a FormArray you do the following:

要想使用 FormArray，你要这么做：

1. Define the items (FormControls or FormGroups) in the array.

   在数组中定义条目（FormControl 或 FormGroup）。

2. Initialize the array with items created from data in the data model.

   把这个数组初始化微一组从数据模型中的数据创建的条目。

3. Add and remove items as the user requires.

   根据用户的需求添加或移除这些条目。

In this guide, you define a FormArray for Hero.addresses and let the user add or modify addresses (removing addresses is your homework).

在本章中，你为 Hero.addresses 定义了一个 FormArray，并且让用户添加或修改这些住址（移除住址功能请课后自行实现）。

You’ll need to redefine the form model in the HeroDetailComponent constructor, which currently only displays the first hero address in an address FormGroup.

你需要在 HeroDetailComponent 的构造函数中重新定义表单模型，它现在只用 FormGroup 显示第一个英雄住址。

From address to secret lairs

从住址到秘密小屋（Secret Lair）

From the user's point of view, heroes don't have addresses. Addresses are for mere mortals. Heroes have secret lairs! Replace the address FormGroup definition with a secretLairs FormArray definition:

从用户的视角来看，英雄们没有住址。 只有我们凡人才有住址，英雄们拥有的是秘密小屋！ 把 FormGroup 型的住址替换为 FormArray 型的 secretLairs 定义：

Changing the form control name from address to secretLairs drives home an important point: the form model doesn't have to match the data model.

把表单的控件名从 address 改为 secretLairs 时遇到了一个重要问题：表单模型与数据模型不再匹配了。

Obviously there has to be a relationship between the two. But it can be anything that makes sense within the application domain.

显然，必须在两者之间建立关联。但它在应用领域中的意义不限于此，它可以用于任何东西。

Presentation requirements often differ from data requirements. The reactive forms approach both emphasizes and facilitates this distinction.

展现的需求经常会与数据的需求不同。 响应式表单的方法既强调这种差异，也能为这种差异提供了便利。

Initialize the "secretLairs" FormArray

初始化 FormArray 型的 secretLairs

The default form displays a nameless hero with no addresses.

默认的表单显示一个无地址的无名英雄。

You need a method to populate (or repopulate) the secretLairs with actual hero addresses whenever the parent HeroListComponent sets the HeroDetailComponent.hero input property to a new Hero.

你需要一个方法来用实际英雄的地址填充（或重新填充）secretLairs， 而不用管父组件 HeroListComponent 何时把输入属性 HeroDetailComponent.hero 设置为一个新的 Hero。

The following setAddresses method replaces the secretLairs FormArray with a new FormArray, initialized by an array of hero address FormGroups.

下面的 setAddresses 方法把 secretLairs 数组替换为一个新的 FormArray，使用一组表示英雄地址的 FormGroup 来进行初始化。

Notice that you replace the previous FormArray with the FormGroup.setControl method, not with setValue. You're replacing a control, not the value of a control.

注意，你使用**FormGroup.setControl 方法**，而不是 setValue 方法来设置前一个 FormArray。 你所要替换的是控件，而不是控件的值。

Notice also that the secretLairs FormArray contains FormGroups, not Addresses.

还要注意，secretLairs 数组中包含的是**FormGroup，而不是 Address。

Get the FormArray

获取 FormArray

The HeroDetailComponent should be able to display, add, and remove items from the secretLairs FormArray.

HeroDetailComponent 应该能从 secretLairs 中显示、添加和删除条目。

Use the FormGroup.get method to acquire a reference to that FormArray. Wrap the expression in a secretLairs convenience property for clarity and re-use.

使用 FormGroup.get 方法来获取到 FormArray 的引用。 把这个表达式包装进一个名叫 secretLairs 的便捷属性中来让它更清晰，并供复用。

Display the FormArray

显示 FormArray

The current HTML template displays a single address FormGroup. Revise it to display zero, one, or more of the hero's address FormGroups.

当前 HTML 模板显示单个的地址 FormGroup。 要把它修改成能显示 0、1 或更多个表示英雄地址的 FormGroup。

This is mostly a matter of wrapping the previous template HTML for an address in a <div> and repeating that <div> with *ngFor.

要改的部分主要是把以前表示地址的 HTML 模板包裹进一个 <div> 中，并且使用 *ngFor 来重复渲染这个 <div>。

The trick lies in knowing how to write the *ngFor. There are three key points:

诀窍在于要知道如何编写 *ngFor。主要有三点：

1. Add another wrapping <div>, around the <div> with *ngFor, and set its formArrayName directive to "secretLairs". This step establishes the secretLairs FormArray as the context for form controls in the inner, repeated HTML template.

   在 *ngFor 的 <div> 之外套上另一个包装 <div>，并且把它的 formArrayName 指令设为 "secretLairs"。 这一步为内部的表单控件建立了一个 FormArray 型的 secretLairs 作为上下文，以便重复渲染 HTML 模板。

2. The source of the repeated items is the FormArray.controls, not the FormArray itself. Each control is an address FormGroup, exactly what the previous (now repeated) template HTML expected.

   这些重复条目的数据源是 FormArray.controls 而不是 FormArray 本身。 每个控件都是一个 FormGroup 型的地址对象，与以前的模板 HTML 所期望的格式完全一样。

3. Each repeated FormGroup needs a unique formGroupName which must be the index of the FormGroup in the FormArray. You'll re-use that index to compose a unique label for each address.

   每个被重复渲染的 FormGroup 都需要一个独一无二的 formGroupName，它必须是 FormGroup 在这个 FormArray 中的索引。 你将复用这个索引，以便为每个地址组合出一个独一无二的标签。

Here's the skeleton for the secret lairs section of the HTML template:

下面是 HTML 模板中秘密小屋部分的代码骨架：

Here's the complete template for the secret lairs section:

这里是秘密小屋部分的完整模板：

Add a new lair to the FormArray

把新的小屋添加到 FormArray 中

Add an addLair method that gets the secretLairs FormArray and appends a new address FormGroup to it.

添加一个 addLair 方法，它获取 secretLairs 数组，并把新的表示地址的 FormGroup 添加到其中。

Place a button on the form so the user can add a new secret lair and wire it to the component's addLair method.

把一个按钮放在表单中，以便用户可以添加新的秘密小屋，并把它传给组件的 addLair 方法。

Be sure to add the type="button" attribute. In fact, you should always specify a button's type. Without an explicit type, the button type defaults to "submit". When you later add a form submit action, every "submit" button triggers the submit action which might do something like save the current changes. You do not want to save changes when the user clicks the Add a Secret Lair button.

务必确保添加了 type="button" 属性。 事实上，你应该总是指定按钮的 type。 如果不明确指定类型，按钮的默认类型就是“submit”（提交）。 当你稍后添加了表单提交的动作时，每个“submit”按钮都是触发一次提交操作，而它将可能会做一些处理，比如保存当前的修改。 你显然不会希望每当用户点击“Add a Secret Lair”按钮时就保存一次。

Try it!

试试看！

Back in the browser, select the hero named "Magneta". "Magneta" doesn't have an address, as you can see in the diagnostic JSON at the bottom of the form.

回到浏览器中，选择名叫“Magneta”的英雄。 "Magneta"没有地址，你会在表单底部的诊断用 JSON 中看到这一点。

Click the "Add a Secret Lair" button. A new address section appears. Well done!

点击“Add a Secret Lair”按钮，一个新的地址区就出现了，干得好！

Remove a lair

移除一个小屋

This example can add addresses but it can't remove them. For extra credit, write a removeLair method and wire it to a button on the repeating address HTML.

这个例子可以添加地址，但是还不能移除它们。 作为练习，你可以自己写一个 removeLair 方法，并且把它关联到地址 HTML 模板的一个按钮上。

{@a observe-control}

Observe control changes

监视控件的变化

Angular calls ngOnChanges when the user picks a hero in the parent HeroListComponent. Picking a hero changes the HeroDetailComponent.hero input property.

每当用户在父组件 HeroListComponent 中选取了一个英雄，Angular 就会调用一次 ngOnChanges。 选取英雄会修改输入属性 HeroDetailComponent.hero。

Angular does not call ngOnChanges when the user modifies the hero's name or secret lairs. Fortunately, you can learn about such changes by subscribing to one of the form control properties that raises a change event.

当用户修改英雄的名字或秘密小屋时，Angular并不会调用 ngOnChanges。 幸运的是，你可以通过订阅表单控件的属性之一来了解这些变化，此属性会发出变更通知。

These are properties, such as valueChanges, that return an RxJS Observable. You don't need to know much about RxJS Observable to monitor form control values.

有一些属性，比如 valueChanges，可以返回一个 RxJS 的 Observable 对象。 要监听控件值的变化，你并不需要对 RxJS 的 Observable 了解更多。

Add the following method to log changes to the value of the name FormControl.

添加下列方法，以监听姓名这个 FormControl 中值的变化。

Call it in the constructor, after creating the form.

在构造函数中调用它，就在创建表单的代码之后：

The logNameChange method pushes name-change values into a nameChangeLog array. Display that array at the bottom of the component template with this *ngFor binding:

logNameChange 方法会把一条改名记录追加到 nameChangeLog 数组中。 用 *ngFor 绑定在组件模板的底部显示这个数组：

Return to the browser, select a hero (e.g, "Magneta"), and start typing in the name input box. You should see a new name in the log after each keystroke.

返回浏览器，选择一个英雄（比如“Magneta”），并开始在姓名输入框中键入。 你会看到，每次按键都会记录一个新名字。

When to use it

什么时候用它

An interpolation binding is the easier way to display a name change. Subscribing to an observable form control property is handy for triggering application logic within the component class.

插值表达式绑定时显示姓名变化比较简单的方式。 在组件类中订阅表单控件属性变化的可观察对象以触发应用逻辑则是比较难的方式。

{@a save}

Save form data

保存表单数据

The HeroDetailComponent captures user input but it doesn't do anything with it. In a real app, you'd probably save those hero changes. In a real app, you'd also be able to revert unsaved changes and resume editing. After you implement both features in this section, the form will look like this:

HeroDetailComponent 捕获了用户输入，但没有用它做任何事。 在真实的应用中，你可能要保存这些英雄的变化。 在真实的应用中，你还要能丢弃未保存的变更，然后继续编辑。 在实现完本节的这些特性之后，表单是这样的：

Save

保存

In this sample application, when the user submits the form, the HeroDetailComponent will pass an instance of the hero data model to a save method on the injected HeroService.

在这个范例应用中，当用户提交表单时，HeroDetailComponent 会把英雄实例的数据模型传给所注入进来的 HeroService 的一个方法来进行保存。

This original hero had the pre-save values. The user's changes are still in the form model. So you create a new hero from a combination of original hero values (the hero.id) and deep copies of the changed form model values, using the prepareSaveHero helper.

原始的 hero 中有一些保存之前的值，用户的修改仍然是在表单模型中。 所以你要根据原始英雄（根据 hero.id 找到它）的值组合出一个新的 hero 对象，并用 prepareSaveHero 助手来深层复制变化后的模型值。

Address deep copy

地址的深层复制

Had you assigned the formModel.secretLairs to saveHero.addresses (see line commented out), the addresses in saveHero.addresses array would be the same objects as the lairs in the formModel.secretLairs. A user's subsequent changes to a lair street would mutate an address street in the saveHero.

你已经把 formModel.secretLairs 赋值给了 saveHero.addresses（参见注释掉的部分）， saveHero.addresses 数组中的地址和 formModel.secretLairs 中的会是同一个对象。 用户随后对小屋所在街道的修改将会改变 saveHero 中的街道地址。

The prepareSaveHero method makes copies of the form model's secretLairs objects so that can't happen.

但 prepareSaveHero 方法会制作表单模型中的 secretLairs 对象的复本，因此实际上并没有修改原有对象。

Revert (cancel changes)

丢弃（撤销修改）

The user cancels changes and reverts the form to the original state by pressing the Revert button.

用户可以撤销修改，并通过点击 Revert 按钮来把表单恢复到原始状态。

Reverting is easy. Simply re-execute the ngOnChanges method that built the form model from the original, unchanged hero data model.

丢弃很容易。只要重新执行 ngOnChanges 方法就可以拆而，它会重新从原始的、未修改过的 hero 数据模型来构建出表单模型。

Buttons

按钮

Add the "Save" and "Revert" buttons near the top of the component's template:

把“Save”和“Revert”按钮添加到组件模板的顶部：

The buttons are disabled until the user "dirties" the form by changing a value in any of its form controls (heroForm.dirty).

这些按钮默认是禁用的，直到用户通过修改任何一个表单控件的值“弄脏”了表单中的数据（即 heroForm.dirty）。

Clicking a button of type "submit" triggers the ngSubmit event which calls the component's onSubmit method. Clicking the revert button triggers a call to the component's revert method. Users now can save or revert changes.

点击一个类型为 "submit" 的按钮会触发 ngSubmit 事件，而它会调用组件的 onSubmit 方法。 点击“Revert”按钮则会调用组件的 revert 方法。 现在，用户可以保存或放弃修改了。

This is the final step in the demo. Try the .

这是本演示的最后一步。 去试试吧。

Summary

小结

• How to create a reactive form component and its corresponding template.

  如何创建一个响应式表单控件及其对应的模板。

• How to use FormBuilder to simplify coding a reactive form.

  如何使用 FormBuilder 来简化响应式表单的编码工作。

• Grouping FormControls.

  分组 FormControl。

• Inspecting FormControl properties.

  审查 FormControl 的属性。

• Setting data with patchValue and setValue.

  使用 patchValue 和 setValue 设置数据。

• Adding groups dynamically with FormArray.

  使用 FormArray 动态添加控件组。

• Observing changes to the value of a FormControl.

  监听 FormControl 中值的变化。

• Saving form changes.

  保存表单中的更改。

{@a source-code}

The key files of the final version are as follows:

最终版中的核心文件如下：

You can download the complete source for all steps in this guide from the Reactive Forms Demo live example.

你可以到响应式表单在线例子中下载本章所有步骤的完整代码。