Polish attribute-directive.jade
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Yang Lin
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@ -4,7 +4,7 @@ block includes
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:marked
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An **Attribute** directive changes the appearance or behavior of a DOM element.
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**属性**型指令用于改变一个DOM元素的外观或行为。
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**属性**型指令用于改变一个 DOM 元素的外观或行为。
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:marked
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@ -13,17 +13,17 @@ block includes
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# 目录
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* [Directives overview](#directive-overview)
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* [指令概览](#directive-overview)
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[指令概览](#directive-overview)
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* [Build a simple attribute directive](#write-directive)
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* [创建简单的属性型指令](#write-directive)
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[创建简单的属性型指令](#write-directive)
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* [Apply the attribute directive to an element in a template](#apply-directive)
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* [把这个属性型指令应用到模板中的元素](#apply-directive)
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[应用属性型指令到模板中的元素](#apply-directive)
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* [Respond to user-initiated events](#respond-to-user)
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* [响应用户引发的事件](#respond-to-user)
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[响应用户引发的事件](#respond-to-user)
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* [Pass values into the directive using data binding](#bindings)
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* [使用数据绑定把值传到指令中](#bindings)
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[使用数据绑定把值传到指令中](#bindings)
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* [Bind to a second property](#second-property)
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* [绑定第二个属性](#second-property)
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[绑定第二个属性](#second-property)
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试试<live-example>在线例子</live-example>。
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@ -37,14 +37,14 @@ a#directive-overview
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There are three kinds of directives in Angular:
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在Angular中有三种类型的指令：
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在 Angular 中有三种类型的指令：
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1. Components—directives with a template.
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1. 组件 - 拥有模板的指令
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组件 — 拥有模板的指令
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1. Structural directives—change the DOM layout by adding and removing DOM elements.
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1. 结构型指令 - 通过添加和移除DOM元素改变DOM格局的指令
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结构型指令 — 通过添加和移除 DOM 元素改变 DOM 布局的指令
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1. Attribute directives—change the appearance or behavior of an element.
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1. 属性型指令 - 改变元素显示和行为的指令。
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属性型指令 — 改变元素显示和行为的指令。
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*Components* are the most common of the three directives.
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You saw a component for the first time in the [QuickStart](../quickstart.html) example.
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@ -55,12 +55,12 @@ a#directive-overview
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*Structural Directives* change the structure of the view. Two examples are [NgFor](template-syntax.html#ngFor) and [NgIf](template-syntax.html#ngIf)
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in the [Template Syntax](template-syntax.html) page.
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*结构型*指令会通过添加/删除DOM元素来更改DOM树布局。[NgFor](template-syntax.html#ngFor)和[NgIf](template-syntax.html#ngIf)就是两个最熟悉的例子。
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*结构型*指令修改视图的结构。例如，[NgFor](template-syntax.html#ngFor) 和 [NgIf](template-syntax.html#ngIf)。
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*Attribute directives* are used as attributes of elements. The built-in [NgStyle](template-syntax.html#ngStyle) directive in the [Template Syntax](template-syntax.html) page, for example,
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can change several element styles at the same time.
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*属性型*指令改变一个元素的外观或行为。比如，内置的[NgStyle](template-syntax.html#ngStyle)指令可以同时修改元素的多种样式。
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*属性型*指令改变一个元素的外观或行为。例如，内置的 [NgStyle](template-syntax.html#ngStyle) 指令可以同时修改元素的多个样式。
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.l-main-section
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a#write-directive
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@ -74,8 +74,8 @@ a#write-directive
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the attribute.
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The controller class implements the desired directive behavior.
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属性型指令至少需要一个带有`@Directive`装饰器的控制器类。该装饰器指定了一个选择器，用于指出与此指令相关联的属性名字。
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控制器类实现了指令需要具备的行为。
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属性型指令至少需要一个带有`@Directive`装饰器的控制器类。该装饰器指定了一个用于标识属性的选择器。
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控制器类实现了指令需要的指令行为。
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This page demonstrates building a simple attribute
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directive to set an element's background color
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@ -86,14 +86,14 @@ a#write-directive
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:marked
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Technically, a directive isn't necessary to simply set the background color. Style binding can set styles as follows:
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实际上，指令并不一定只是简单的设置背景颜色。样式绑定可以像下面这样设置样式：
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实际上，简单地设置背景颜色并不需要再定义一个指令。样式绑定可以像下面这样设置样式：
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+makeExample('attribute-directives/ts/app/app.component.1.html','p-style-background')
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:marked
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Read more about [style binding](template-syntax.html#style-binding) on the [Template Syntax](template-syntax.html) page.
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参见[模板语法](template-syntax.html)章的[样式绑定](template-syntax.html#style-binding)。
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更多信息，见[模板语法](template-syntax.html)的[样式绑定](template-syntax.html#style-binding)。
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For a simple example, though, this will demonstrate how attribute directives work.
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@ -107,7 +107,7 @@ a#write-directive
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Follow the [setup](setup.html) instructions for creating a new project
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named <span ngio-ex>attribute-directives</span>.
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按照[搭建本地开发环境](setup.html)的说明，创建一个项目文件夹<span ngio-ex>attribute-directives</span>。
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按照[开发环境](setup.html)的说明，创建一个项目文件夹<span ngio-ex>attribute-directives</span>。
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:marked
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Create the following source file in the indicated folder with the following code:
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@ -120,37 +120,35 @@ block highlight-directive-1
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:marked
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The `import` statement specifies symbols from the Angular `core`:
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`import`语句指定了从Angular的`core`库导入的一些符号。
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`import`语句指定了从 Angular 的`core`库导入的一些符号。
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1. `Directive` provides the functionality of the `@Directive` decorator.
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1. `Directive`提供`@Directive`装饰器功能。
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`Directive`提供`@Directive`装饰器功能。
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1. `ElementRef` [injects](dependency-injection.html) into the directive's constructor
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1. `ElementRef` [注入](dependency-injection.html)到指令构造函数中。
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so the code can access the DOM element.
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这样代码可以访问DOM元素。
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`ElementRef`[注入](dependency-injection.html)到指令构造函数中。
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这样代码可以访问 DOM 元素。
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1. `Input` allows data to flow from the binding expression into the directive.
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1. `Input`将数据从绑定表达式传达到指令中。
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`Input`将数据从绑定表达式传达到指令中。
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1. `Renderer` allows the code to change the DOM element's style.
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1. `Renderer` 让代码可以改变DOM元素的样式。
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`Renderer` 让代码可以改变 DOM 元素的样式。
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Next, the `@Directive` decorator function contains the directive metadata in a configuration object
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as an argument.
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然后，`@Directive`装饰器函数以“配置对象”参数的形式，包含了指令的元数据。
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然后，`@Directive`装饰器函数以配置对象参数的形式，包含了指令的元数据。
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:marked
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`@Directive` requires a CSS selector to identify
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the HTML in the template that is associated with the directive.
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属性型指令的`@Directive`装饰器需要一个css选择器，以便从模板中识别出关联到这个指令的HTML。
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`@Directive`装饰器需要一个 CSS 选择器，以便从模板中识别出关联到这个指令的 HTML。
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The [CSS selector for an attribute](https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors)
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@ -158,39 +156,36 @@ block highlight-directive-1
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Here, the directive's selector is `[myHighlight]`.
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Angular will locate all elements in the template that have an attribute named `myHighlight`.
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[css中的attribute选择器](https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors)就是属性名称加方括号。
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这里，指令的选择器是`[myHighlight]`，Angular将会在模板中找到带有`myHighlight`这个属性的元素。
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[用于 attribute 的 CSS 选择器](https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors)就是属性名称加方括号。
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这里，指令的选择器是`[myHighlight]`，Angular 将会在模板中找到所有带`myHighlight`属性的元素。
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.l-sub-section
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:marked
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### Why not call it "highlight"?
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### 为什么不直接叫做"highlight"？
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### 为什么不直接叫做 "highlight"？
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Though *highlight* is a more concise name than *myHighlight* and would work,
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a best practice is to prefix selector names to ensure
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they don't conflict with standard HTML attributes.
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This also reduces the risk colliding with third-party directive names.
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理论上，*highlight*是一个比*myHighlight*更好的名字，而且在这里它确实能工作。
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但是最佳实践是在选择器名字前面添加前缀，以确保它们不会与标准HTML属性冲突。
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尽管*highlight* 是一个比 *myHighlight* 更简洁的名字，而且它确实也能工作。
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但是最佳实践是在选择器名字前面添加前缀，以确保它们不会与标准 HTML 属性冲突。
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它同时减少了与第三方指令名字发生冲突的危险。
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Make sure you do **not** prefix the `highlight` directive name with **`ng`** because
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that prefix is reserved for Angular and using it could cause bugs that are difficult to diagnose. For a simple demo, the short prefix, `my`, helps distinguish your custom directive.
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确认你**不会**给自己的`highlight`指令添加**`ng`**前缀。
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那个前缀属于Angular，使用它可能导致无法检测的问题。比如，这个简短的前缀`my`可以帮助你区分自定义指令。
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确认你**没有**给`highlight`指令添加**`ng`**前缀。
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那个前缀属于 Angular，使用它可能导致难以诊断的 bug。例如，这个简短的前缀`my`可以帮助你区分自定义指令。
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p
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| After the #[code @Directive] metadata comes the directive's controller class, called #[code HighlightDirective], which contains the logic for the directive.
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| Exporting #[code HighlightDirective] makes it accessible to other components.
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p
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| #[code @Directive]元数据的后面就是指令的控制器类，叫做#[code HighlightDirective]，它包括了指令的工作逻辑。
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+ifDocsFor('ts')
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| Exporting #[code HighlightDirective] makes it accessible to other components.
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+ifDocsFor('ts')
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| 导出#[code HighlightDirective]以便让它可以被其它组件访问。
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| 导出#[code HighlightDirective]以便让它可以被其它组件访问。
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:marked
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Angular creates a new instance of the directive's controller class for
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each matching element, injecting an Angular `ElementRef` and `Renderer`
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@ -198,8 +193,9 @@ p
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`ElementRef` is a service that grants direct access to the DOM element
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through its `nativeElement` property and `Renderer` allows the code to set the element style.
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Angular会为每个被指令匹配上的元素创建一个该指令控制器类的实例，并把Angular的`ElementRef`和`Renderer`注入进它的构造函数。
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`ElementRef`是一个服务，它赋予我们直接访问DOM元素的能力。通过它的`nativeElement`属性和`Renderer`服务，我们可以设置元素的样式。
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Angular 会为每个匹配的元素创建一个指令控制器类的实例，并把 Angular 的`ElementRef`和`Renderer`注入进构造函数。
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`ElementRef`是一个服务，它赋予我们通过它的`nativeElement`属性直接访问 DOM 元素的能力。
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`Renderer`服务允许通过代码设置元素的样式。
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.l-main-section
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a#apply-directive
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@ -213,7 +209,7 @@ a#apply-directive
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In Angular terms, the `<p>` element will be the attribute **host**.
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要使用这个新的`HighlightDirective`，创建一个模板，把这个指令作为属性应用到一个段落(`p`)元素上。
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用Angular的话说，`<p>`元素就是这个属性型指令的**宿主**。
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用 Angular 的话说，`<p>`元素就是这个属性型指令的**宿主**。
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p
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| Put the template in its own
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code #[+adjExPath('app.component.html')]
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@ -226,15 +222,15 @@ p
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:marked
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Now reference this template in the `AppComponent`:
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现在，引用`AppComponent`的模板：
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现在，在`AppComponent`中引用这个模板：
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+makeExample('attribute-directives/ts/app/app.component.ts',null,'app/app.component.ts')
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:marked
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Next, add an `import` statement to fetch the `Highlight` directive and
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add that class to the `declarations` NgModule metadata. This way Angular
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recognizes the directive when it encounters `myHighlight` in the template.
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接下来，添加了一个`import`语句来获得'Highlight'指令类，并把这个类添加到`AppComponent`组件的`declarations`数组中。
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这样，当Angular在模板中遇到`myHighlight`时，就能认出这是指令了。
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接下来，添加了一个`import`语句来获得`Highlight`指令类，并把这个类添加到 NgModule 元数据的`declarations`数组中。
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这样，当 Angular 在模板中遇到`myHighlight`时，就能认出这是指令了。
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+makeExample('attribute-directives/ts/app/app.module.ts',null,'app/app.module.ts')
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Did you remember to add the directive to the the `declarations` attribute of `@NgModule`? It is easy to forget!
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你记着设置`@NgModule`的`declarations`数组了吗？它很容易被忘掉。
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Open the console in the browser tools and look for an error like this:
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@ -269,8 +264,8 @@ figure.image-display
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in the array, Angular knows to check the import statements and from there,
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to go to `highlight.directive.ts` to find out what `myHighlight` does.
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Angular检测到你正在尝试绑定到*某些东西*，但它不认识。所以它在`declarations`元数据数组中查找。
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把`HighlightDirective`列在元数据的这个数组中，Angular就会检查对应的导入语句，从而找到`highlight.directive.ts`，并了解`myHightlight`的功能。
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Angular 检测到你正在尝试绑定到*某些东西*，但它不认识。所以它在`declarations`元数据数组中查找。
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把`HighlightDirective`列在元数据的这个数组中，Angular 就会检查对应的导入语句，从而找到`highlight.directive.ts`，并了解`myHightlight`的功能。
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:marked
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To summarize, Angular found the `myHighlight` attribute on the `<p>` element. It created
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injecting a reference to the element into the constructor
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where the `<p>` element's background style is set to yellow.
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总结：Angular在`<p>`元素上发现了一个`myHighlight`属性。
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总结：Angular 在`<p>`元素上发现了一个`myHighlight`属性。
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然后它创建了一个`HighlightDirective`类的实例，并把所在元素的引用注入到了指令的构造函数中。
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在构造函数中，我们把`<p>`元素的背景设置为了黄色。
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我们需要：
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1. detecting when the user hovers into and out of the element.
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1. 检测用户的鼠标啥时候进入和离开这个元素。
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检测用户的鼠标何时进入和离开这个元素。
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2. responding to those actions by setting and clearing the highlight color.
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2. 通过设置和清除高亮色来响应这些操作。
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通过设置和清除高亮色来响应这些操作。
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To do this, you can apply the `@HostListener` !{_decorator} to methods which are called when an event is raised.
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把`host`属性加入指令的元数据中，并给它一个配置对象，用来指定两个鼠标事件，并在它们被触发时，调用指令中的方法：
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把`@HostListener`装饰应用到事件触发时需调用的方法。
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+makeExample('attribute-directives/ts/app/highlight.directive.2.ts','host')(format=".")
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@ -316,11 +311,11 @@ a#respond-to-user
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:marked
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The `@HostListener` !{_decorator} refers to the DOM element that hosts an attribute directive, the `<p>` in this case.
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`@HostListener`装饰器引用的是我们这个属性型指令的宿主元素，在这个例子中就是`<p>`。
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`@HostListener`装饰器引用属性型指令的宿主元素，在这个例子中就是`<p>`。
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It is possible to attach event listeners by manipulating the host DOM element directly, but
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可以通过直接操纵DOM元素的方式给宿主DOM元素挂上一个事件监听器，但是
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可以通过直接操纵 DOM 元素的方式给宿主 DOM 元素附加一个事件监听器，但是
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there are at least three problems with such an approach:
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@ -328,15 +323,15 @@ a#respond-to-user
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1. You have to write the listeners correctly.
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1. 必须正确的书写事件监听器。
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必须正确的书写事件监听器。
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|
||||
1. The code must *detach* the listener when the directive is destroyed to avoid memory leaks.
|
||||
|
||||
1. 当指令被销毁的时候，必须*摘掉*事件监听器，否则就会导致内存泄露。
|
||||
当指令被销毁的时候，必须*拆卸*事件监听器，否则会导致内存泄露。
|
||||
|
||||
1. Talking to DOM API directly isn't a best practice.
|
||||
|
||||
1. 必须直接和DOM API打交道，但正如我们学过的那样，应该避免这样做。
|
||||
必须直接和 DOM API 打交道，应该避免这样做。
|
||||
|
||||
:marked
|
||||
Now implement the two mouse event handlers:
|
||||
|
|
@ -366,7 +361,7 @@ a#respond-to-user
|
|||
We run the app and confirm that the background color appears as we move the mouse over the `p` and
|
||||
disappears as we move out.
|
||||
|
||||
运行本应用，就可以确认：当把鼠标移到`p`上的时候，背景色就出现了，而移开的时候，它消失了。
|
||||
运行本应用并确认：当把鼠标移到`p`上的时候，背景色就出现了，而移开的时候，它消失了。
|
||||
figure.image-display
|
||||
img(src="/resources/images/devguide/attribute-directives/highlight-directive-anim.gif" alt="Second Highlight")
|
||||
.l-main-section
|
||||
|
|
@ -374,7 +369,7 @@ a#bindings
|
|||
:marked
|
||||
## Pass values into the directive using data binding
|
||||
|
||||
## 通过绑定来传递值到指令中
|
||||
## 使用数据绑定向指令传递值
|
||||
|
||||
Currently the highlight color is hard-coded within the directive. That's inflexible.
|
||||
A better practice is to set the color externally with a binding as follows:
|
||||
|
|
@ -385,7 +380,7 @@ a#bindings
|
|||
:marked
|
||||
You can extend the directive class with a bindable **input** `highlightColor` property and use it to highlight text.
|
||||
|
||||
我们将给指令类增加一个可绑定**输入**属性`highlightColor`，当需要高亮文本的时候，就用它。
|
||||
我们将给指令类增加一个可绑定**输入**属性`highlightColor`，用它来加亮文本。
|
||||
|
||||
Here is the final version of the class:
|
||||
|
||||
|
|
@ -398,7 +393,7 @@ a#input
|
|||
The new `highlightColor` property is called an *input* property because data flows from the binding expression into the directive.
|
||||
Notice the `@Input()` #{_decorator} applied to the property.
|
||||
|
||||
新的`highlightColor`属性被称为“输入”属性，这是因为数据流是从绑定表达式到这个指令的。
|
||||
新的`highlightColor`属性被称为*输入*属性，因为数据是从绑定表达式流入指令中。
|
||||
注意，在定义这个属性的时候，我们调用了`@Input()`#{_decoratorCn}。
|
||||
|
||||
+makeExcerpt('app/highlight.directive.ts', 'color')
|
||||
|
|
@ -409,19 +404,19 @@ a#input
|
|||
Without this input metadata Angular rejects the binding.
|
||||
See the [appendix](#why-input) below for more information.
|
||||
|
||||
`@Input`把元数据添加到了类上，这让`highlightColor`能被以`myHighlight`为别名进行绑定。
|
||||
必须添加这个input元数据，否则Angular会拒绝绑定。
|
||||
参见下面的[附录](#why-input)来了解为何如此。
|
||||
`@Input`向类添加元数据，使`highlightColor`属性能以`myHighlight`为别名进行绑定。
|
||||
没有这个输入元数据，Angular 会拒绝绑定。
|
||||
更多信息，见下面的[附录](#why-input)。
|
||||
.l-sub-section
|
||||
:marked
|
||||
### @Input(_alias_)
|
||||
|
||||
### @Input(_别名_)
|
||||
### @Input（_别名_）
|
||||
|
||||
Currently, the code **aliases** the `highlightColor` property with the attribute name by
|
||||
passing `myHighlight` into the `@Input` #{_decorator}:
|
||||
|
||||
当前，代码通过将`myHighlight`传递到`@Input`装饰器，把`myHighlight`属性**别名**到属性名字上。
|
||||
当前，代码通过将`myHighlight`传递到`@Input`装饰器，把`myHighlight`属性作为`highlightColor`属性的**别名**。
|
||||
|
||||
+makeExcerpt('app/highlight.directive.ts', 'color', '')
|
||||
:marked
|
||||
|
|
@ -440,8 +435,8 @@ a#input
|
|||
Now that you're getting the highlight color as an input, modify the `onMouseEnter()` method to use
|
||||
it instead of the hard-coded color name and define red as the default color.
|
||||
|
||||
现在，通过输入型属性得到了高亮的颜色，然后修改`onMouseEnter()`来使用它代替硬编码的那个颜色名。
|
||||
我们还把红色定义为默认颜色，以便在用户忘了绑定颜色时作为备用。
|
||||
现在，通过输入型属性得到了高亮的颜色，然后修改`onMouseEnter()`来使用它代替硬编码的那个颜色名，
|
||||
并将红色定义为默认颜色。
|
||||
|
||||
+makeExcerpt('attribute-directives/ts/app/highlight.directive.ts', 'mouse-enter', '')
|
||||
:marked
|
||||
|
|
@ -456,7 +451,7 @@ a#input
|
|||
:marked
|
||||
### Where is the templated *color* property?
|
||||
|
||||
### 模板的*color*属性在哪里？
|
||||
### 模板的 *color* 属性在哪里？
|
||||
|
||||
You may notice that the radio button click handlers in the template set a `color` property
|
||||
and the code is binding that `color` to the directive.
|
||||
|
|
@ -470,7 +465,7 @@ a#input
|
|||
Browser debugging reveals that Angular dynamically added a `color` property
|
||||
to the runtime instance of the `AppComponent`.
|
||||
|
||||
在浏览器中调试就会发现，Angular在`AppComponent`的运行期实例上添加了一个`color`属性。
|
||||
在浏览器中调试就会发现，Angular 在`AppComponent`的运行期实例上添加了一个`color`属性。
|
||||
|
||||
This is *convenient* behavior but it is also *implicit* behavior that could be confusing.
|
||||
For clarity, consider adding the `color` property to the `AppComponent`.
|
||||
|
|
@ -505,7 +500,7 @@ a#second-property
|
|||
The `defaultColor` property has a setter that overrides the hard-coded default color, "red".
|
||||
You don't need a getter.
|
||||
|
||||
`defaultColor`属性是一个setter函数，它代替了硬编码的默认颜色“red”。不需要getter函数。
|
||||
`defaultColor`属性是一个 setter 函数，它代替了硬编码的默认颜色 “red”。不需要 getter 函数。
|
||||
|
||||
How do you bind to it? The app is already using `myHighlight` attribute name as a binding target.
|
||||
|
||||
|
|
@ -517,7 +512,7 @@ a#second-property
|
|||
|
||||
记住，*组件也是指令*。
|
||||
只要需要，就可以通过把它们依次串在模板中来为组件添加多个属性绑定。
|
||||
下面这个例子中就把`a`、`b`、`c`属性设置为了字符串字面量'a', 'b', 'c'。
|
||||
下面这个例子中就把`a`、`b`、`c`属性设置为了字符串字面量'a'、'b'、'c'。
|
||||
code-example(format="." ).
|
||||
<my-component [a]="'a'" [b]="'b'" [c]="'c'"><my-component>
|
||||
:marked
|
||||
|
|
@ -548,13 +543,20 @@ figure.image-display
|
|||
|
||||
本章介绍了如何：
|
||||
- [Build a simple **attribute directive** to attach behavior to an HTML element](#write-directive)
|
||||
- [构建一个简单的**属性型指令**来为一个HTML元素添加行为](#write-directive)，
|
||||
|
||||
[构建一个简单的**属性型指令**来为一个 HTML 元素添加行为](#write-directive)。
|
||||
|
||||
- [Use that directive in a template](#apply-directive).
|
||||
- [在模板中使用那个指令](#apply-directive)，
|
||||
|
||||
[在模板中使用那个指令](#apply-directive)。
|
||||
|
||||
- [Respond to **events** to change behavior based on an event](#respond-to-user).
|
||||
- [响应**事件**，以便基于事件改变行为](#respond-to-user)，
|
||||
|
||||
[响应**事件**，以便基于事件改变行为](#respond-to-user)。
|
||||
|
||||
- [Use **binding** to pass values to the attribute directive](#bindings).
|
||||
- 以及[使用**绑定**来把值传给属性型指令](#bindings)。
|
||||
|
||||
以及[使用**绑定**来把值传给属性型指令](#bindings)。
|
||||
|
||||
The final source:
|
||||
|
||||
|
|
@ -582,12 +584,12 @@ a#why-input
|
|||
:marked
|
||||
### Appendix: Input properties
|
||||
|
||||
### 附录：Input属性
|
||||
### 附录：输入属性
|
||||
|
||||
In this demo, the `highlightColor` property is an ***input*** property of
|
||||
`HighlightDirective`.
|
||||
|
||||
本例中, `highlightColor`属性是`HighlightDirective`指令的一个***input***属性。
|
||||
本例中, `highlightColor`属性是`HighlightDirective`指令的一个***输入***属性。
|
||||
|
||||
You've seen properties in bindings before but never had to declare them as anything. Why now?
|
||||
|
||||
|
|
@ -595,58 +597,55 @@ a#why-input
|
|||
|
||||
Angular makes a subtle but important distinction between binding **sources** and **targets**.
|
||||
|
||||
|
||||
Angular在绑定的**源**和**目标**之间有一个巧妙但重要的区别。
|
||||
Angular 在绑定的**源**和**目标**之间有一个巧妙但重要的区别。
|
||||
|
||||
In all previous bindings, the directive or component property was a binding ***source***.
|
||||
A property is a *source* if it appears in the template expression to the ***right*** of the equals (=).
|
||||
|
||||
在以前的所有绑定中，指令或组件的属性都是绑定***源***。
|
||||
如果属性出现在了模板表达式等号(=)的***右侧***，它就是一个*源*。
|
||||
如果属性出现在了模板表达式等号 (=) 的***右侧***，它就是一个*源*。
|
||||
|
||||
A property is a *target* when it appears in **square brackets** ([ ]) to the **left** of the equals (=)
|
||||
as it is does when binding to the `myHighlight` property of the `HighlightDirective`.
|
||||
|
||||
如果它出现在了**方括号**([ ])中，并且出现在等号(=)的**左侧**，它就是一个*目标*……
|
||||
如果它出现在了**方括号** ([ ]) 中，并且出现在等号 (=) 的**左侧**，它就是一个*目标*，
|
||||
就像在绑定到`HighlightDirective`的`myHighlight`属性时所做的那样。
|
||||
+makeExample('attribute-directives/ts/app/app.component.html','pHost')(format=".")
|
||||
:marked
|
||||
The 'color' in `[myHighlight]="color"` is a binding ***source***.
|
||||
A source property doesn't require a declaration.
|
||||
|
||||
|
||||
`[myHighlight]="color"`中的'color'就是绑定***源***。
|
||||
源属性不需要特别声明。
|
||||
`[myHighlight]="color"`中的 'color' 是绑定***源***。
|
||||
源属性不需要声明。
|
||||
|
||||
The 'myHighlight' in `[myHighlight]="color"` *is* a binding ***target***.
|
||||
You must declare it as an *input* property or
|
||||
Angular rejects the binding with a clear error.
|
||||
|
||||
`[myHighlight]="color"`中的'myHighlight'就是绑定***目标***。
|
||||
必须把它定义为一个*Input*属性，否则，Angular就会拒绝这次绑定，并给出一个明确的错误。
|
||||
`[myHighlight]="color"`中的 'myHighlight' 是绑定***目标***。
|
||||
必须把它定义为一个*输入*属性，否则，Angular 就会拒绝绑定，并给出一个明确的错误。
|
||||
|
||||
Angular treats a *target* property differently for a good reason.
|
||||
A component or directive in target position needs protection.
|
||||
|
||||
Angular这样区别对待*目标*属性有充分的理由。
|
||||
Angular 这样区别对待*目标*属性有充分的理由。
|
||||
作为目标的组件或指令需要保护。
|
||||
|
||||
Imagine that `HighlightDirective` did truly wonderous things in a
|
||||
popular open source project.
|
||||
|
||||
假想一下，`HighlightDirective`真是一个好东西。
|
||||
我们优雅的把它当作礼物送给全世界。
|
||||
假想一下，在一个开源项目中，`HighlightDirective`做了些很精彩的事。
|
||||
|
||||
Surprisingly, some people — perhaps naively —
|
||||
start binding to *every* property of the directive.
|
||||
Not just the one or two properties you expected them to target. *Every* property.
|
||||
That could really mess up your directive in ways you didn't anticipate and have no desire to support.
|
||||
|
||||
出乎意料的是，有些人(可能因为太天真)开始绑定到这个指令中的*每一个*属性。
|
||||
出乎意料的是，有些人（可能因为太天真）开始绑定到这个指令中的*每一个*属性。
|
||||
不仅仅只是我们预期为绑定目标的那一两个属性，而是*每一个*。
|
||||
这可能会扰乱指令的工作方式 —— 我们既不想这样做也不想支持它们这样做。
|
||||
|
||||
The ***input*** declaration ensures that consumers of your directive can only bind to
|
||||
the properties of the public API but nothing else.
|
||||
|
||||
于是，这种*输入*声明可以确保指令的消费者只能绑定到公开API中的属性，其它的都不行。
|
||||
于是，这种*输入*声明可以确保指令的消费者只能绑定到公开 API 中的属性，其它的都不行。
|
||||
|
|
|
|||
Loading…
Reference in New Issue