anchor.diff:      所以我们要把`hero`属性**替换**成`selectedHero`属性。
   
     +makeExample('toh-2/ts/src/app/app.component.ts', 'selected-hero', 'src/app/app.component.ts (selectedHero)')
  +  
     :marked
       The hero names should all be unselected before the user picks a hero, so
       you won't initialize the `selectedHero` as you did with `hero`.
  
positive.code:     :marked
        Don't forget the asterisk (`*`) in front of `ngIf`.
        
        记住，`ngIf`前导星号 (`*`) 是语法中的重要组成部分。
  
    :marked
      The app no longer fails and the list of names displays again in the browser.
  
negative.code:     :marked
        Read more about the `[class]` binding in the [Template Syntax](../guide/template-syntax.html#ngClass "Template syntax: NgClass") guide.
  
        关于`[class]`绑定的更多信息，参见[模板语法](../guide/template-syntax.html#ngClass "Template syntax: NgClass")。
  
    :marked
      The final version of the `<li>` looks like this:
      
    +makeExample('toh-2/ts/src/app/app.component.1.html', 'class-selected-2', 'app.component.ts (styling each hero)')(format=".")
  
    :marked
  