如何直接在角度4的模板绑定中增加变量？

Question

我有以下对象：

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 
     } 
    ]; 

，我喜欢这样的循环这样的HTML：

<ng-template ngFor let-person="$implicit" let-variable [ngForOf]="people"> 
      {{variable + 30}} 
    <ng-template/> 

我的问题是，是否有有一个局部变量，并通过30增加它的一种方式对于模板绑定中的ngfor中的每个元素？而不是有方法来增加？

，我有递增从方法变量的问题是，我得到以下错误：

Error: ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked

Answer 1

<ng-template ngFor let-person="$implicit" let-variable [ngForOf]="people" let-i="index"> 
    <p *ngIf="i == 0">{{variable + 30}}</p> 
    <p *ngIf="i > 0">{{variable + (30*i)}}</p> 
<ng-template/> 

通过这个你从0开始总长度的指标。