anchor.diff:    this `currency` pipe expression,
     
     >**[管道Pipes](pipes.html)** - 这种服务会转换值以供显示。我们可以把管道放在模板中，以增强用户体验。比如这个`currency`管道表达式，
  +  
   <div style="margin-left:40px">
   code-example(language="javascript" linenumbers=".").
     price | currency:'USD':true
  
positive.code:   >**[Testing](../testing/index.html)** - Angular provides a testing library for "unit testing" our application parts as they
    interact with the Angular framework.
  
    >**[Testing](../testing/index.html)** - Angular提供了一个用于对我们应用中的各个部分进行“单元测试”的测试库，就像它们与Angular框架交互时一样。
  
negative.code:   ... ***and*** between parent and child components
    
    ……在父组件与子组件的通讯中***也同样如此***。
    
  <br clear="all">
  
  .l-main-section
  <a id="directive"></a>
  :marked
    ## The Directive
    
    ## 指令
      
  figure
    img(src="/resources/images/devguide/architecture/directive.png" alt="父与子" style="float:left; width:150px; margin-left:-40px;margin-right:10px" )
  :marked
    Our Angular templates are *dynamic*. When Angular renders them, it transforms the DOM 
    according to the instructions given by a **directive**.
    
    我们的Angular模板是*动态的*。当Angular渲染它们时，它会根据**指令**提供的操作指南对DOM进行修改。
    
    A directive is a class with directive metadata. In TypeScript we'd apply the `@Directive` decorator
    to attach metadata to the class.
    
    指令是一个带有“指令元数据”的类。在TypeScript中，我们要通过`@Directive`装饰器把元数据附加到类上。
    
  <br clear="all">
  :marked
    We already met one form of directive: the component. A component is a *directive-with-a-template*
  