title: Array with select option in Angular and Typescript
body: <p>I display 51 questions with their related answers on a page. 
  Both information come from one web-service call. </p>
  
  <pre><code>&lt;tbody&gt;
     &lt;tr *ngFor="let QuestionOption of questions; trackBy: trackQuestionById; let i = index;"&gt;
     &lt;th scope="row"&gt;{{QuestionOption.id}}&lt;/th&gt;
     &lt;td&gt;{{QuestionOption.name}} {{QuestionOption.description}}
      &lt;/p&gt;
       &lt;select  class="form-control"  name="selectAnswer" [(ngModel)]="answer[i]"&gt;
       &lt;option *ngFor="let answers of QuestionOption.Answers" [ngValue]="answers.id"&gt;{{answers.description}}&lt;/option&gt;
      &lt;/p&gt;
     &lt;/td&gt;
  &lt;/tr&gt;
  &lt;/tbody&gt;
  </code></pre>
  
  <p>on the typescript code I try the following:</p>
  
  <pre><code>answer: Answer[];
  this.answer = new Array&lt;Answer&gt;();
  </code></pre>
  
  <p>The type Answer has multiple fields like: Id, Name, Score, Description</p>
  
  <p>What is not working is that I always have get the Id into the answer[i]
  but I want to have the id in the field answer[i].id</p>
  
  <p>If i change the </p>
  
  <pre><code>[(ngModel)]="answer[i]"
  </code></pre>
  
  <p>into </p>
  
  <pre><code>[(ngModel)]="answer[i].id"
  </code></pre>
  
  <p>I get the following exception:
  ERROR TypeError: "_co.caaAnswer[_v.context.index] is undefined"</p>
  
  <p>I also tried: </p>
  
  <pre><code>[(ngModel)]="answer[i]?.id"
  </code></pre>
  
  <p>So is it correct to use answer[i] ? and then in the option I should somehow assign to answer[i].id the selected value. If so somebody can help how to do it.</p>
  
  <p>Any help is appreciated! Thanks a lot.
  augeres</p>