anchor.diff:    
     * We designed our service to return a !{_Promise} and our component to get our data from the !{_Promise}.
     
  -  * 我们把服务设计为返回Promise，组件从Promise中获取数据。
  +  * 我们把服务设计为返回承诺，组件从承诺中获取数据。
   
     Run the <live-example></live-example> for this part.
     
  
positive.code: :marked
    As a result of our change to `HeroService`, we're now setting `this.heroes` to a !{_Promise} rather than an array of heroes. 
    
    在修改了`HeroService`之后，我们还要把`this.heroes`替换为一个Promise，而不再是一个英雄数组。
    
    We have to change our implementation to *act on the !{_Promise} when it resolves*.
    When the !{_Promise} resolves successfully, *then* we will have heroes to display.
    
    我们得修改这个实现，把它变成*基于Promise*的，并在承诺的事情被解决时再行动。
    一旦Promise被成功解决，我们就会显示英雄数据。
    
    We pass our callback function as an argument to the !{_Promise}'s **then** method:
    
    我们把回调函数作为参数传给Promise对象的**then**函数：
    
  +makeExample('toh-4/ts/app/app.component.ts', 'get-heroes', 'app/app.component.ts (getHeroes - revised)')(format=".")
  
  
negative.code: :marked
    Update the `HeroService` with this !{_Promise}-returning `getHeroes` method:
    
    把`HeroService`的`getHeroes`方法改写为返回承诺的形式：
    
  +makeExample('toh-4/ts/app/hero.service.ts', 'get-heroes', 'app/hero.service.ts (excerpt)')(format=".")
  
  