title: How to increment variable directly in template binding in angular 4?
body: <p>I have the following object:</p>
  
  <pre><code>  this.people = [{
          name: 'Douglas  Pace',
          title: 'Parcelivery Nailed The Efficiency',
          content: 'Since I installed this app, its always help me book every tickets I need like flight, concert, ' +
            'movie or hotel. I don\'t need to install different app for different ticket. The payment is also very easy',
          image: '../../assets/img/profile_pics/profile_pic.jpg',
          rate: '4.5',
          classActive: 'testimonials__selected-visible',
          active: true
        },
        {
          name: 'Naseebullah  Ahmadi',
          title: 'Parcelivery Nailed The Efficiency',
          content: 'Since I installed this app, its always help me book every tickets I need like flight, concert, ' +
            'movie or hotel. I don\'t need to install different app for different ticket. The payment is also very easy',
          image: '../../assets/img/profile_pics/profile_pic.jpg',
          rate: '4.5',
          classActive: '',
          active: false
        },
        {
          name: 'Haseebullah Ahmadi',
          title: 'Parcelivery Nailed The Efficiency',
          content: 'Since I installed this app, its always help me book every tickets I need like flight, concert, ' +
            'movie or hotel. I don\'t need to install different app for different ticket. The payment is also very easy',
          image: '../../assets/img/profile_pics/profile_pic.jpg',
          rate: '4.5',
          classActive: '',
          active: false
        }
      ];
  </code></pre>
  
  <p>and I am looping this in html like so:</p>
  
  <pre><code>  &lt;ng-template ngFor let-person="$implicit" let-variable [ngForOf]="people"&gt;
            {{variable + 30}}
     &lt;ng-template/&gt;
  </code></pre>
  
  <p>My question is, is there a way of having a local variable and incrementing it by 30 for each element inside the ngfor in template binding? Rather than having methods to do the incrementing?</p>
  
  <p>The issue that I have with incrementing the variable from methods is that i get the following error:</p>
  
  <blockquote>
    <p>Error: ExpressionChangedAfterItHasBeenCheckedError: Expression has
    changed after it was checked</p>
  </blockquote>