anchor.diff:    
     2. 如果没写`@SkipSelf`装饰器的话，Angular就会抛出一个循环依赖错误。
   
  -    `Cannot instantiate cyclic dependency! (BethComponent -> Parent -> BethComponent)`
  -
  -    `不能创建循环依赖实例！(BethComponent -> Parent -> BethComponent)`
  +  `Cannot instantiate cyclic dependency! (BethComponent -> Parent -> BethComponent)`
  +
  +  `不能创建循环依赖实例！(BethComponent -> Parent -> BethComponent)`
   
     Here's *Alice*, *Barry* and family in action:
   
  
positive.code: .l-main-section
  :marked
    ## External module configuration
    We often register providers in the `NgModule` rather than in the root application component.
      
    We do this when (a) we expect the service to be injectable everywhere
    or (b) we must configure another application global service _before it starts_.
    
    We see an example of the second case here, where we configure the Component Router with a non-default
    [location strategy](../guide/router.html#location-strategy) by listing its provider 
    in the `providers` list of the `AppModule`.
    
  +makeExample('cb-dependency-injection/ts/app/app.module.ts','providers','app/app.module.ts (providers)')(format='.') 
  
  
negative.code:   
    [Define providers with object literals](#object-literals)
  
    [使用对象字面量定义提供商](#object-literals)
  
    [Provider token alternatives](#tokens)
  
  