title: Angular 2 - ngFor-Iteration --> click-event doesn´t works on single Array-Entry of ngFor
body: <p>I have an Array with defined answers for a survey-question in data model in component.ts of relevant template.
  The template rendering for a <code>&lt;li&gt;</code>-tag for each answer (in Array) with iteration of this Array via *ngFor-Directive works great.</p>
  
  <p>Now I want to implement a click-event for toggle an active-state for <strong>EACH</strong> of this <code>&lt;li&gt;</code>-tags (multiple-choise answer).</p>
  
  <p>The following markup makes all items of the Array (all answers) active, <strong>NOT</strong> only the single <code>li</code>-tag, which I have clicked. That's my problem,where  I am looking forward to solve it with the support of the community.</p>
  
  <p><strong>HTML-template</strong></p>
  
  <pre><code>&lt;ul&gt;
    &lt;li *ngFor="let answer of questions.quest_1.answers, let i=index;" (click)="isActive = !isActive" [ngClass]="{'active': isActive}"&gt;{{answer}}&lt;/li&gt;
  &lt;/ul&gt; 
  </code></pre>
  
  <p><strong>relevant component Code</strong></p>
  
  <pre><code>questions = {
   quest_1: {
   quest: 'my question...',
   answers: ['answer A', 'answer B', 'answer C', 'answer D'],
  },}
  </code></pre>
  
  <p>for toggle:</p>
  
  <pre><code>isActive: boolean = false;
  </code></pre>
  
  <p>I tried to implement the index on click-event in HTML, but it doesn´t works too.
  Thanks in advance</p>