first draft translation of dependency-injection.jade is completed.
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@ -1169,19 +1169,27 @@ a(id="parent-tree")
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Imagine one branch of a component hierarchy: *Alice* -> *Barry* -> *Carol*.
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Both *Alice* and *Barry* implement the `Parent` *class-interface*.
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想象一下一个组件层次的一个分支为:*Alice* -> *Barry* -> *Carol*。
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*Alice*和*Barry*两个都实现`父级`*类-接口*。
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*Barry* is the problem. He needs to reach his parent, *Alice*, and also be a parent to *Carol*.
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That means he must both *inject* the `Parent` *class-interface* to get *Alice* and
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*provide* a `Parent` to satisfy *Carol*.
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*Barry*是一个问题。他需要访问它的父级*Alice*,同时他也是*Carol*的父级。这个意味着它必须同时*注入*`父级`*类-接口*来得到*Alice*,和*提供*一个`父级`来满足*Carol*。
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Here's *Barry*:
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下面是*Barry*:
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','barry','parent-finder.component.ts (BarryComponent)')(format='.')
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:marked
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*Barry*'s `providers` array looks just like [*Alex*'s](#alex-providers).
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If we're going to keep writing [*alias providers*](#useexisting) like this we should create a [helper function](#provideparent).
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*Barry*的`providers`数组看起来像[*Alex*的](#alex-providers).
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如果我们一直要像这样编写[*别名providers*](#useexisting)的话,我们应该建立一个[帮助函数](#provideparent)。
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For now, focus on *Barry*'s constructor:
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眼下,集中主意*Barry*的构造函数:
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+makeTabs(
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'cb-dependency-injection/ts/app/parent-finder.component.ts, cb-dependency-injection/ts/app/parent-finder.component.ts',
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'barry-ctor, carol-ctor',
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@ -1190,65 +1198,104 @@ a(id="parent-tree")
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:marked
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It's identical to *Carol*'s constructor except for the additional `@SkipSelf` decorator.
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除了添加了一个额外的`@SkipSelf`外,它和*Carol*的构造函数一样。
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`@SkipSelf` is essential for two reasons:
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使用`@SkipSelf`主要是为了下面两个原因:
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1. It tell the injector to start its search for a `Parent` dependency in a component *above* itself,
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which *is* what parent means.
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1. 它告诉注入器从一个在自己*上面*的组件开始搜索一个`Parent`依赖。
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2. Angular throws a cyclic dependency error if we omit the `@SkipSelf` decorator.
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2. 如果我们缺少`@SkipSelf`装饰器的话,Angular会抛出一个循环依赖错误。
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`Cannot instantiate cyclic dependency! (BethComponent -> Parent -> BethComponent)`
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`不能创建循环依赖实例!(BethComponent -> Parent -> BethComponent)`
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Here's *Alice*, *Barry* and family in action:
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这里是*Alice*,*Barry*和该家庭的实际代码:
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figure.image-display
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img(src="/resources/images/cookbooks/dependency-injection/alice.png" alt="Alice in action")
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a(id="parent-token")
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:marked
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### The *Parent* class-interface
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### *父级*类-接口
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We [learned earlier](#class-interface) that a *class-interface* is an abstract class used as an interface rather than as a base class.
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我们[之前学到](#class-interface):一个*类-接口*是一个抽象类,被当做一个接口来使用,而非被当做基本类使用。
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Our example defines a `Parent` *class-interface* .
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我们的例子定义了一个`Parent`*类-接口*。
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','parent','parent-finder.component.ts (Parent class-interface)')(format='.')
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:marked
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The `Parent` *class-interface* defines a `name` property with a type declaration but *no implementation*.,
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The `name` property is the only member of a parent component that a child component can call.
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Such a narrowing interface helps decouple the child component class from its parent components.
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该`Parent` *类-接口*定义了一个`Name`属性,它有一个类型声明,但是*没有实现*,该`name`是该父级组件的子级组件们唯一能调用的属性。
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这样一个窄的接口帮助分离子级类和它的父级组件。
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A component that could serve as a parent *should* implement the *class-interface* as the `AliceComponent` does:
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一个能当做父级的组件*应该*实现*类-接口*,和下面的`AliceComponent`的做法一样:
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','alice-class-signature','parent-finder.component.ts (AliceComponent class signature)')(format='.')
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:marked
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Doing so adds clarity to the code. But it's not technically necessary.
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Although the `AlexComponent` has a `name` property (as required by its `Base` class)
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its class signature doesn't mention `Parent`:
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这样做增加了代码的清晰度。但是技术并不一定需要它。虽然`AlexComponent`有一个`name`属性(被他的`基本`类要求),它的类签名并不提及`Parent`。
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','alex-class-signature','parent-finder.component.ts (AlexComponent class signature)')(format='.')
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.l-sub-section
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:marked
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The `AlexComponent` *should* implement `Parent` as a matter of proper style.
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It doesn't in this example *only* to demonstrate that the code will compile and run without the interface
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为了正确的代码风格,该`AlexComponent`*应该*实现`Parent`。在这个例子里面它不这样,仅仅是为了演示在没有该接口的情况下,该代码会被编译并执行。
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a(id="provideparent")
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:marked
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### A *provideParent* helper function
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### 一个*privdeParent*帮助函数
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Writing variations of the same parent *alias provider* gets old quickly,
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especially this awful mouthful with a [*forwardRef*](#forwardref):
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编写同一个父级的各种*别名provider*很快就变得很啰嗦,在用[*forwardRef](#forwardRef)的时候尤其绕口:
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','alex-providers')(format='.')
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:marked
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We can extract that logic into a helper function like this:
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我们可以像这样把这个逻辑提取到一个帮助函数里面:
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','provide-the-parent')(format='.')
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:marked
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Now we can add a simpler, more meaningful parent provider to our components:
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现在我们就可以为我们的组件添加一个简单点的,更加直观的父级provider:
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','alice-providers')(format='.')
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:marked
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We can do better. The current version of the helper function can only alias the `Parent` *class-interface*.
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Our application might have a variety of parent types, each with its own *class-interface* token.
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我们可以做的更好。当前版本的帮助函数只能为`父级`*类-接口*提供别名。我们的应用程序可能有很多类型的父级,每个父级有自己的*类-接口*令牌。
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Here's a revised version that defaults to `parent` but also accepts an optional second parameter for a different parent *class-interface*.
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这里是一个修改版本,默认接受一个`父级`,但是同时接受一个可选的第二个参数,可以用来指定一个不同的父级*类-接口*。
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','provide-parent')(format='.')
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:marked
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And here's how we could use it with a different parent type:
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下面是我们如何使用它添加一个不同类型的父级:
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','beth-providers')(format='.')
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:marked
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@ -1256,30 +1303,50 @@ a(id="forwardref")
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.l-main-section
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:marked
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## Break circularities with a forward class reference (*forwardRef*)
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## 使用一个转寄类引用(*forwardRef*)来来打破循环
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The order of class declaration matters in TypeScript.
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We can't refer directly to a class until it's been defined.
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在TypeScript里面,类声明的顺序是有重要关系的。在一个类没有被定义之前,我们不能引用它。
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This isn't usually a problem, especially if we adhere to the recommended *one class per file* rule.
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But sometimes circular references are unavoidable.
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We're in a bind when class 'A refers to class 'B' and 'B' refers to 'A'.
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One of them has to be defined first.
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它通常不是一个问题,特别是当我们遵循*一个类一个文件*规则的时候。
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但是有时候循环引用可能不能避免。当一个类*A引用类B*,同时'B'引用'A'的时候,我们就遇到困境了:它们中间的一个必须要先定义。
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The Angular `forwardRef` function creates an *indirect* reference that Angular can resolve later.
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Angular的`forwardRef`函数建立一个*间接地*引用,Angular可以随后解析。
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The *Parent Finder* sample is full of circular class references that are impossible to break.
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这个*父级寻找器*例子是到处都是类循环引用,我们无法打破。
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In the [*Alex/Cathy* example](#known-parent) above:
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在上面的[*Alex/Cathy*例子](#known-parent)中:
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* the `AlexComponent` lists the `CathyComponent` in its component metadata `directives` array
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so it can display *Cathy* in its template.
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* `AlexComponent`在它的组件元数据`指令`数值里面列出`CathyComponent`,这样它可以在自己的模板中显示*Cathy*。
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* the `CathyComponent` constructor injects the parent `AlexComponent` which means that the `alex` parameter
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of its constructor has the `AlexComponent` type.
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* `CathyComponent`的构造函数注入父级`AlexComponent`,这样的话,构造函数参数`alex`是`AlexComponent`类型。
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*Alex* refers to *Cathy* and *Cathy* refers to *Alex*. We're stuck. We must define one of them first.
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*Alex* 引用了*Cathy*,同时,*Cathy*引用了*Alex*。我们被卡住了。我们必须要先它们中的一个。
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We defined *Alex* first and built its `C_DIRECTIVES` array with a forward reference to *Cathy*:
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我们先定义了*Alex*,使用一个*Cathy*的转寄引用,建筑了它的`C_DIRECTIVES`数值:
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','C_DIRECTIVES','parent-finder.component.ts (C_DIRECTIVES)')(format='.')
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:marked
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.l-sub-section
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@ -1287,15 +1354,23 @@ a(id="forwardref")
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Defining *Alex* and *Cathy* in separate files won't help.
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*Alex* would have to import *Cathy* and *Cathy* would have to import *Alex*.
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在单独的文件里面定义*Alex*和*Cathy*并不能帮忙。*Alex*必须要导入*Cathy*,*Cathy*必须要导入*Alex*。
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We *had* to define *Alex* first because,
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while we can add `forwardRef(CathyComponent)` to *Alex*'s `directives` array,
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we can't write `public alex: forwardRef(AlexComponent))` in *Cathy*'s constructor.
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我们*被迫*先定义*Alex*,因为我们可以添加`forwardRef(CathyComponent)`到*Alex*的`指令`数组里面,但是我们不能在*Cathy*的构造函数里面使用`public alex: forwardRef(AlexComponent))`。
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:marked
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We face a similar dilemma when a class makes *a reference to itself*
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as does the `AlexComponent` in its `providers` array.
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The `providers` array is a property of the `@Component` decorator function which must
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appear *above* the class definition.
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当一个类使用*一个自己的引用*的时候,我们面临同样的窘境,就像`AlexComponent`的`provdiers`数组里的困境一样。
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该`providers`数组是一个`@Component`装饰器函数的一个属性,它必须要在类定义*之前*出现。
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Again we break the circularity with `forwardRef`:
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我们又一次使用`forwardRef`来打破该循环:
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+makeExample('cb-dependency-injection/ts/app/parent-finder.component.ts','alex-providers','parent-finder.component.ts (AlexComponent providers)')(format='.')
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:marked
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