title: Set Required to a custom Angular2 dropdown component
body: <p>I have a form that has few input fields and a custom dropdown. The question is: Can I set my-custom-dropdown component to be required?</p>
  
  <p>My form looks something like this:</p>
  
  <pre><code>&lt;form name="myform" (ngSubmit)="onSubmit()" #myform="ngForm"&gt;
      &lt;!-- other fields omitted for brevity --&gt;
      &lt;my-custom-dropdown name="someValue" #someValue="ngModel" [(ngModel)]="model.someValue"&gt;&lt;/my-custom-dropdown&gt;
  
      &lt;button type="submit"&gt;Submit&lt;/button&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>My dropdown component is basically a custom component that looks something like this:</p>
  
  <pre><code>&lt;div&gt;
      &lt;label&gt;
          Set some value
      &lt;/label&gt;
      &lt;p class="form-control-static"&gt;{{model.name}}&lt;/p&gt;
      &lt;ul&gt;
          &lt;my-custom-dropdown-item *ngFor="let option of options; let i = index" [(value)]="model" [option]="option"&gt;&lt;/my-custom-dropdown-item&gt;
      &lt;/ul&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And finally I have items of a dropdown like this: </p>
  
  <pre><code>&lt;li&gt;
      &lt;!-- some structural and styling stuff omitted for brevity --&gt;
      {{option.name}}
  &lt;/li&gt;
  </code></pre>
  
  <p>I'm using the latest version of Angular2. I did not include Typescript files but long story short, my-custom-dropdown component implements ControlValueAccessor.</p>