ngIf 可以在 Angular 1.5 中引用嵌套 ngFor 中的变量。 如何在 Angular 10 中实现相同的功能？

Question

The following code works in Angular 1.5. The <tr> element will only be rendered if the 'showFields' flag for that row key is enabled.

<table>
  <ng-container *ngIf="showFields[row.key]">
    <tr *ngFor="let row of rows">
      <td>{{row.key}}</td>
      <td>{{row.value}}</td>
    </tr>
  </ng-container>
</table>

Note that the 'row' variable from the ngFor is visible to the enclosing ngIf. This no longer works in Angular 2+ because the scope of the ngFor variable is now confined to the element. How could I achieve the same effect?

Answer 1

You could just switch the ngFor and ngIf , like so:

<table>
  <ng-container *ngFor="let row of rows">
    <tr *ngIf="showFields[row.key]">
        <td>{{row.key}}</td>
        <td>{{row.value}}</td>
    </tr>
  </ng-container>
</table>

Instead of using a separate showFields boolean array, you could also think about adding a new property showField to the row object, then you can simply check *ngIf="row.showField" , which prevents out of bounds exceptions.