*ngIf and *ngFor on same element causing error

Question

I\'m having a problem with trying to use Angular\'s *ngFor and *ngIf on the same element.

When trying to loop through the collection in th

Answer 1

Angular v2 doesn't support more than one structural directive on the same element.
As a workaround use the <ng-container> element that allows you to use separate elements for each structural directive, but it is not stamped to the DOM.

<ng-container *ngIf="show">
  <div *ngFor="let thing of stuff">
    {{log(thing)}}
    <span>{{thing.name}}</span>
  </div>
</ng-container>

<ng-template> (<template> before Angular v4) allows to do the same but with a different syntax which is confusing and no longer recommended

<ng-template [ngIf]="show">
  <div *ngFor="let thing of stuff">
    {{log(thing)}}
    <span>{{thing.name}}</span>
  </div>
</ng-template>

Answer 2

As @Zyzle mentioned, and @Günter mentioned in a comment (https://github.com/angular/angular/issues/7315), this is not supported.

With

<ul *ngIf="show">
  <li *ngFor="let thing of stuff">
    {{log(thing)}}
    <span>{{thing.name}}</span>
  </li>
</ul>

there are no empty <li> elements when the list is empty. Even the <ul> element does not exist (as expected).

When the list is populated, there are no redundant container elements.

The github discussion (4792) that @Zyzle mentioned in his comment also presents another solution using <template> (below I'm using your original markup ‐ using <div>s):

<template [ngIf]="show">
  <div *ngFor="let thing of stuff">
    {{log(thing)}}
    <span>{{thing.name}}</span>
  </div>
</template>

This solution also does not introduce any extra/redundant container elements.

Answer 3

This will work but the element will still in the DOM.

.hidden {
    display: none;
}

---

<div [class.hidden]="!show" *ngFor="let thing of stuff">
    {{log(thing)}}
    <span>{{thing.name}}</span>
</div>

Answer 4

<div *ngFor="let thing of show ? stuff : []">
  {{log(thing)}}
  <span>{{thing.name}}</span>
</div>

Answer 5

You can't use multiple structural directive on same element. Wrap your element in ng-template and use one structural directive there

Answer 6

On other solution might be to put an empty array in your for loop in the case where you don't want to display it

<div *ngFor="let thing of show ? stuff : []">

Where "stuff" is an array of "thing" and "show" the boolean to display or not the content