我的 ngIf Else 在 Angular 6 中没有按预期工作

Question

I have this code that should show the data when the variable blockusers is not empty (which works), but should show the Nought, nil, nada, nothing, zero, zilch and zip WHEN it is empty, which does not work... and I can not see the mistake anywhere.

<div class="col-lg-9" *ngIf="blockusers; else zipZeroResults">
 I'm getting results and I will show them!
</div>
<ng-template #zipZeroResults>
  Nought, nil, nada, nothing, zero, zilch and zip.
</ng-template>

Thanks for your help

Answer 1

You are doing a truthy check on an array which will always return true if the array reference itself is not null or undefined . It will even return true if the array is empty (no elements).

Your truthy check should be done on the length of the array. Then if the array is empty (length = 0) it will evaluate the expression to false which is what you are expecting.

*ngIf="blockusers?.length; else zipZeroResults"

This will check on length but not throw an error if the array itself is undefined or null (using the Safe Navigation Operator ).