如何直接在角度4的模板綁定中增加變量？

Question

我有以下對象：

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 
     } 
    ]; 

，我喜歡這樣的循環這樣的HTML：

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

我的問題是，是否有有一個局部變量，並通過30增加它的一種方式對於模板綁定中的ngfor中的每個元素？而不是有方法來增加？

，我有遞增從方法變量的問題是，我得到以下錯誤：

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/> 

通過這個你從0開始總長度的指標。