anchor.diff:    The `save` method persists hero name changes using the hero service
     `update` method and then navigates back to the previous view:
     
  -  `save`方法使用hero服务的`update`方法来持久化对英雄名字的修改，然后导航回前一个页面：
  +  `save`方法使用hero服务的`update`方法来持久化对英雄名字的修改，然后导航回前一个视图：
   
   +makeExcerpt('app/hero-detail.component.ts', 'save')
   
  
positive.code:   Review the sample source code in the <live-example></live-example> for this chapter.
    Verify that we have the following structure:
    
    在<live-example>在线例子</live-example>中回顾本章的范例代码。
    验证我们是否得到了如下结构：
  
  block filetree
  
negative.code: 
    The `*ngFor` repeats *hero* objects from the component's `heroes` property. No surprise there.
    
    `*ngFor`从该组件的`heroes`属性重复获取*hero*对象。这也没啥特别的。
  
    But, as we'll soon see, the `heroes` property is now !{_an} *!{_Observable}* of hero !{_array}s, rather than just a hero !{_array}.
    The `*ngFor` can't do anything with !{_an} `!{_Observable}` until we flow it through the `async` pipe (`AsyncPipe`).
  