Jonas Jonas - 7 months ago 453
Javascript Question

Counting up in ngFor - Angular 2

I have a problem counting up the ngFor Loop in Angular 2. Im trying to develop a grid that has 3 columns and a dynamic amount of rows. I would like to loop through my array and add the elements from left to right and every three elements it should jump to the next row. Im using Ionic Framework 2.0.

My code looks like this:

<ion-row *ngFor="#m of movies; #i = index" (click)="movieTapped(m)">
<ion-col width-33>
<div class="row responsive-md">
<img [src]="m.Poster" width="100%" />
{{m.Title}} <br>
Rating: {{m.imdbRating}}<br>
Rated: {{m.Rated}}<br>
Released: {{m.Year}}<br>
</div>
</ion-col>
<ion-col width-33>
<div class="row responsive-md">
<img [src]="m.Poster" width="100%" />
</div>
</ion-col>
<ion-col width-33>
<div class="row responsive-md">
<img [src]="m.Poster" width="100%" />
</div>
</ion-col>
</ion-row>


Hope you can help me out.

Cheers!

Answer

If you don't want to format your data structure into groups of columns (which I can understand) then you can still render columns 3 per row. For this you will need to precalculate additional helper array of row indexes, e.g. [0,1,2,3]. Number of the elements in the array should be equal to the number of ion-row you want to render. So in your controller constructor function you can do something like this:

this.rows = Array.from(Array(Math.ceil(this.movies.length / 3)).keys())

Then in template you will have two ngFor loops:

<ion-row *ngFor="#i of rows" (click)="movieTapped(m)">
  <ion-col *ngFor="#m of movies | slice:(i*3):(i+1)*3" width-33>
    <div class="row responsive-md">
      <img [src]="m.Poster" width="100%" /> {{m.Title}}
      <br> Rating: {{m.imdbRating}}
      <br> Rated: {{m.Rated}}
      <br> Released: {{m.Year}}
    </div>
  </ion-col>
</ion-row>

That's it. Depending on the current row index slice pipe renders necessary items per row.

Here is simplified demo: http://plnkr.co/edit/WyEfryGccFrJvwm6jExM?p=preview