ANGULAR 2/4 : call function for each row in NgFor

问题:

i'm learning AngularJS, and i need some help.

I have a template like this

    <div *ngFor="let beat of data" (invoke)="myFunction(beat.id)" class="item">
      <div class="item-column-1 inline">
        <div class="item-column-1-container">
          <img class="item-img1" src="/CMP.jpg">
          <p>{{beat.uploader}}</p>
        </div>
      </div>
      <div class="item-column-2 inline">
        <span class="item-title">{{beat.title}}</span>
        <p class="item-score">245 </p>
        <span>#TRAPCHILL</span>
        <p>#TYGA #DRAKE #YOUNG THUG #MIGOS</p>
        <P>Posted: 2 days ago</P>
          <!-- <input (click)="rate(beat.id,1)" alt="beat.id" type="radio" id="star1" name="rating" value="1" /><label class = "full" for="star1" title="{{beat.id}}">1</label>
          <input (click)="rate(beat.id,2)" alt="beat.id" type="radio" id="star2" name="rating" value="2" /><label class = "full" for="star2" title="{{beat.id}}">2</label>
          <input (click)="rate(beat.id,3)" alt="beat.id" type="radio" id="star3" name="rating" value="3" /><label class = "full" for="star3" title="{{beat.id}}">3</label> -->
          <div  (click)="rate(beat.id,1)" class="flamme"></div>
          <div  (click)="rate(beat.id,2)" class="flamme"></div>
          <div  (click)="rate(beat.id,3)" class="flamme"></div>

        <span></span>
      </div>
      <button (click)="play(beat.path)" type="button" name="button">play</button>
      <button (click)="sendMsg()">Send</button>


      <div class="item-column-3 inline">
          <img class="album-cover" src="{{beat.path_img}}" alt="">
      </div>

    </div>

Now, for each data in my ngFor, i want to call a function ( in occurence myFunction(beat.id)), this function will return a number.

i wanna retrieve the number of the return function, for display it in each data of my ngFor...

I've tried to create a directive "invoke", with an output event, and then in my ngAfterContentInit(), i emitted my output, but nothing happened, it's not trigged when my data is loaded.

@Directive({ selector: '[invoke]'})

export class MainComponent implements OnInit {
retrievedObject : any;
src : string;
data : any;
current:any;
rating : any;
countRate : any;
subscription: Subscription;

duration:any;
@Output() invoke:EventEmitter<boolean> = new EventEmitter();
---
ngAfterContentInit() {
  this.invoke.emit(null);
}

myFunction(beat_id){

alert('trigged');
}

So if anybody have a solution.. thank's !

回答1:

this.data = dataFromSomewhere();
this.dataOpt = this.data.map((d) => this.myFunction(d.id));

<div *ngFor="let beat of data; let i=index"  class="item">
  <div>{{dataOpt[i]}}</div>

The pipe variant:

@Pipe({selector: myFunc})
class MyPipy implements PipeTransform {
  transform(val:string) {
    return // do the same calculation here that you would do in `myFunction`;
  }
}

and use it like

<div *ngFor="let beat of data; let i=index"  class="item">
  <div>{{data | myPipe}}</div>

(the pipe needs to be registered in declarations of the module (or in an imported module)

回答2:

Get an array as property on your class. Each time your function is called, set the corresponding item (say i) of this array to the value. And in the template reference the i item of that same array.