title: Angular 4: how to set a default radio button from a list
body: <p>I have a list of 4 items of which one should be selected. </p>
  
  <p>In my component I have: </p>
  
  <pre><code>items = ['item1', 'item2', 'item3', 'item4'];
  currentItem = 'item3'; 
  </code></pre>
  
  <p>The submit of the form is: </p>
  
  <pre><code>onSubmit( form : NgForm ) {
      console.log( 'Before formaction current item = ' + this.currentItem);
      this.currentItem = form.value.item;
      console.log( 'After formaction current item = ' + this.currentItem);
  }
  </code></pre>
  
  <p>My template is: </p>
  
  <pre><code>&lt;div class="form-group"&gt;
    &lt;div class="radio" *ngFor="let item of items"&gt;
      &lt;label&gt;
        &lt;input type="radio" name="item" ngModel [value]="item" [checked]="item === currentItem"&gt; {{ item }}
      &lt;/label&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>How can I set a default? 
  And of course get the value back? </p>