dependency-injection.jade, a little more translation.
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@ -594,62 +594,93 @@ figure.image-display
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img(src="/resources/images/cookbooks/dependency-injection/hero-of-month.png" alt="Hero of the month" width="300px")
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:marked
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It's visually simple: a few properties and the output of a logger. The code behind it gives us plenty to talk about.
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它看起来很简单:一些属性和一个日志output。但是后面的代码给我们很多议论点。
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+makeExample('cb-dependency-injection/ts/app/hero-of-the-month.component.ts','hero-of-the-month','hero-of-the-month.component.ts')
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.l-main-section
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a(id='provide')
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:marked
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#### The *provide* function
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#### *provide*函数
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The imported Angular `provide` function creates an instance of
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the Angular [Provider](../api/core/Provider-class.html) class.
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被导入的Angular `provide`函数新建一个Angular [Provider](../api/core/Provider-class.html)类的实例。
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The `provide` function takes a *token* and a *definition object*.
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The *token* is usually a class but [it doesn't have to be](#tokens).
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该`provide`函数需要一个*令牌*和一个*定义对象*。该*令牌*通常是一个类,但是[他不是一定是](#tokens)
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The *definition* object has one main property, (e.g. `useValue`) that indicates how the provider
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should create or return the provided value.
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该*定义*项目有一个主要属性,(即为`userValue`)来标识该provider应该怎么新建和返回被提供的结果。
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.l-main-section
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a(id='usevalue')
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:marked
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#### useValue - the *value provider*
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#### useValue - *值provider*
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Set the `useValue` property to a ***fixed value*** that the provider can return as the dependency object.
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把一个***固定的值**,也就是该provider可以当作依赖对象返回的值,赋给`userValue`属性。
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Use this technique to provide *runtime configuration constants* such as web-site base addresses and feature flags.
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We often use a *value provider* in a unit test to replace a production service with a fake or mock.
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使用该技巧来提供*运行时间设置常量*,比如网站的基础地址和功能标志等。我们通常在单元测试中使用一个*value provider*,用一个假的或模仿的(服务)来取代一个成品服务。
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The `HeroOfTheMonthComponent` example has two *value providers*.
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The first provides an instance of the `Hero` class;
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the second specifies a literal string resource:
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`HeroOfTheMonthComponent`例子有两个*value providers*。
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第一个提供了一个`Hero`类的实例;第二个指定了一个文字字符串资源:
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+makeExample('cb-dependency-injection/ts/app/hero-of-the-month.component.ts','use-value')(format='.')
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:marked
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The `Hero` provider token is a class which makes sense because the value is a `Hero`
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and the consumer of the injected hero would want the type information.
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该`Hero`provider令牌是一个类,这很合理,因为提供的结果是一个`Hero`,而且使用这个被注入英雄的组件也想要知道这个类型信息。
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The `TITLE` provider token is *not a class*.
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It's a special kind of provider lookup key called an [OpaqueToken](#opaquetoken).
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We often use an `OpaqueToken` when the dependency is a simple value like a string, a number, or a function.
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`TITLE` provider令牌*不是一个类*。它是一个特别类型的provider查询键,名叫[OpaqueToken](#opaquetoken).
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The value of a *value provider* must be defined *now*. We can't create the value later.
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Obviously the title string literal is immediately available.
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The `someHero` variable in this example was set earlier in the file:
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一个*value provider*的值必须要*立刻*定义。我们不能过后定义它的值。很显然,该标题字符串立刻可用。
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该例中的`someHero`变量是于早先,在下面的文件里面定义的:
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+makeExample('cb-dependency-injection/ts/app/hero-of-the-month.component.ts','some-hero')
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:marked
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The other providers create their values *lazily* when they're needed for injection.
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其他providers只在注入需要他们的时候才创建他们值 - *延迟加载*
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.l-main-section
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a(id='useclass')
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:marked
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#### useClass - the *class provider*
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#### useClass - *类provider*
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The `useClass` provider creates and returns new instance of the specified class.
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`userClass` provider创建并返回一个特定类的新实例。
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Use this technique to ***substitute an alternative implementation*** for a common or default class.
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The alternative could implement a different strategy, extend the default class,
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or fake the behavior of the real class in a test case.
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We see two examples in the `HeroOfTheMonthComponent`:
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+makeExample('cb-dependency-injection/ts/app/hero-of-the-month.component.ts','use-class')(format='.')
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:marked
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