anchor.diff:  a#formgroup
   :marked
     ## Add a FormGroup
  +  
  +  ## 添加FormGroup
  +  
     Usually, if you have multiple *FormControls*, you'll want to register 
     them within a parent `FormGroup`.
     This is simple to do. To add a `FormGroup`, add it to the imports section 
     of `hero-detail.component.ts`:
  +  
  +  通常，如果有多个*FormControl*，我们会希望把它们注册进一个父`FormGroup`中。这很容易。只要把它加入`hero-detail.component.ts`的`import`区就可以了。
   
   +makeExample('reactive-forms/ts/src/app/hero-detail-2.component.ts', 'imports','src/app/hero-detail.component.ts')(format=".")
   
   :marked
     In the class, wrap the `FormControl` in a `FormGroup` called `heroForm` as follows:
  +  
  +  在这个类中，把`FormControl`包裹进了一个名叫`heroForm`的`FormGroup`中，代码如下：
   
   +makeExample('reactive-forms/ts/src/app/hero-detail-2.component.ts', 'v2','src/app/hero-detail.component.ts')(format=".")
   
   :marked
     Now that you've made changes in the class, they need to be reflected in the 
     template. Update `hero-detail.component.html` by replacing it with the following.
  +  
  +  现在我们改完了这个类，该把它映射到模板中了。把`hero-detail.component.html`改成这样：
   
   +makeExample('reactive-forms/ts/src/app/hero-detail-2.component.html', 'basic-form','src/app/hero-detail.component.html')(format=".")
   
  
positive.code:   To let Angular know that this is the input that you want to 
    associate to the `name` `FormControl` in the class, 
    you need `[formControl]="name"` in the template on the `<input>`. 
    
  
  .l-sub-section
  
negative.code:   The file exports two classes and two constants. The `Address` 
    and `Hero` classes define the application _data model_. 
    The `heroes` and `states` constants supply the test data. 
    
    这个文件导出两个类和两个常量。`Address`和`Hero`类定义应用的*数据模型*。
    `heroes`和`states`常量提供测试数据。
  
  .l-main-section
  a#create-component
  :marked
    ## Create a _reactive forms_ component
    
    ## 创建*响应式表单*组件
    
    Make a new file called 
    `hero-detail.component.ts` in the `app` directory and import these symbols:
    
    在`app`目录下创建一个名叫`hero-detail.component.ts`的新文件，并且导入下列符号：
  
  +makeExample('reactive-forms/ts/src/app/hero-detail-1.component.ts', 'imports','src/app/hero-detail.component.ts')(format=".")
  
  :marked
    Now enter the `@Component` decorator that specifies the `HeroDetailComponent` metadata:
    
    然后输入这个`@Component`来为`HeroDetailComponent`指定元数据：
  
  +makeExample('reactive-forms/ts/src/app/hero-detail.component.ts', 'metadata','src/app/hero-detail.component.ts (excerpt)')(format=".")
  
  