Angular：NgIf 使用带有多个模板变量的异步管道的正确语法？

Question

With Angular, we can subscribe to an Observable and assign the result of the async pipe to another variable by doing :

    *ngIf="(data$ | async) as data; else loading"

We can check multiple conditions :

    *ngIf="(data1$ | async) && (data2$ | async); else loading"

But what is the correct syntax to verify multiple conditions using Angular "as" Keyword ?

I tried :

    *ngIf="((data1$ | async) as data1) && ((data2$ | async) as data2); else loading"

But I have an issue :

Parser Error: Unexpected token &&, expected identifier, keyword, or string

Answer 1

You can use the object-like syntax.

<ng-container *ngIf="{
  data1: data1$ | async,
  data2: data2$ | async
} as data">
  <div *ngIf="data.data1 && data.data2; else loading"> 
    <span>{{ data.data1 }}</span>
    <span>{{ data.data2 }}</span>
  </div>
</ng-container>
<ng-template #loading> ... </ng-template>

Or, even better, just create a new Observable which combines the other two.

data$ = combineLatest(data1$, data2$).pipe(map(([v1, v2]) => v1 && v2));

Than, just

<div *ngIf="data$ | async; else loading"> 
  ...
</div>
<ng-template #loading> ... </ng-template>

Answer 2

You can try this:

<ng-container *ngIf="{ data1 :data$ | async, data2:data2$ | async} as data;">
<div *ngIf="data.data1 && data.data2; else loading">

  {{data.data1}}
  {{data.data2}}
</div>
<ng-template #loading>
    loading..........
 </ng-template>
</ng-container>