title: Angular 4 array of strings
body: <p>I'm using reactive form,
  I have 2 questions :
  I want to use a array of strings as an input that the user can change directly, I have a data model like this</p>
  
  <pre><code>export class Work {
      toDos: string[];  
  }
  </code></pre>
  
  <p>Q1 : Is it ok to bind a input directly to an array of primitives or should I convert toDos in an array of object with a property name, and always use controls?</p>
  
  <p>Q2 : 
  I tried several think, but I can't find a simple way to make it working :</p>
  
  <pre><code>&lt;div *ngFor="let item of toDos;let index = index;trackBy:trackByIndex;"&gt;
     &lt;input [(ngModel)]="toDos[index]" placeholder="item" name="word{{index}}"&gt;
  &lt;/div&gt;
  
   &lt;button (click)="addItem()" type="button"&gt;Add an 
  Item&lt;/button&gt;
  &lt;div *ngFor="let item of toDos"&gt;
    &lt;label&gt;{{item}}&lt;/label&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>In the component.ts</p>
  
  <pre><code>toDos: string[] =["Todo1","Todo2","Todo3"];
  trackByIndex(index: number, obj: any): any {
     return index;
   }
   addItem() {
     this.toDos.push('0');
   }
  </code></pre>
  
  <p>The add function works ok but the input is not bind and I don't get any errors,
  I can change the value of the input but it's not reflect on {{item}}</p>