Because there's changing animation state quickly, and without this setTimeout you would get error ExpressionChangedAfterItHasBeenCheckedError.

This error would be visible only in ngAfterViewInit.

If you want to open / hide after some actions, you don't have to use setTimeout.

If you don't want to use setTimeout, you could try to use cdRef.detectChanges() after calling the toggle method.

Best Regards,

Damian

It works ! Thank you very much Just one thing : Why do you encapsulate "this.collapse.toggle()" in a setTimeout with 0 ms ?

Thanks

Dear herve,

Just use the @ViewChild decorator to get the handle to the collapse element from the template, and use the toggle method from it.

Please take a look at the below code:

.html:

<button mdbBtn color="primary" class="waves-light" type="button" (click)="test.toggle()" mdbWavesEffect>
        Toggle collapse
      </button>

      <div class="" mdbCollapse #test="bs-collapse">
        <p>Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim
          keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.</p>
      </div>

.ts:

@ViewChild('test') collapse: CollapseComponent;

  ngAfterViewInit() {
    setTimeout(() => {
      this.collapse.toggle();
    }, 0);
  }

Best Regards,

Damian