Data is not rendered with mat-table [datasource] although it exists and is rendered with the "json" pipe

Question

I am implementing a table with mat-table. I want to bind the data source to an array whose data is fetched by an API. When I fetch the data using httpclient and subscribe to the result, the table doesn't render anything.

However, I used the "json" pipe to render the array outside the table, and it works.

Here is my code:

import { HttpClient } from '@angular/common/http';


constructor(private http: HttpClient) {}

displayedColumns: string[] = ['firstname', 'lastname'];
users: any[] = [];

ngOnInit(): void {
  this.http.get('/api/users').subscribe(
    (data) => {
      this.users = data
    },
    (error) => {
      console.log(error)
    }
  );
}

The HTML is as follows:

<table #table mat-table [dataSource]="users" class="mat-elevation-z8">
    <ng-container matColumnDef="firstname">
        <th mat-header-cell *matHeaderCellDef>First Name</th>
        <td mat-cell *matCellDef="let element"> {{element.firstname}} </td>
    </ng-container>
    <ng-container matColumnDef="lastname">
        <th mat-header-cell *matHeaderCellDef>Last Name</th>
        <td mat-cell *matCellDef="let element"> {{element.lastname}} </td>
    </ng-container>

    <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
    <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
</table>

score 1 · Accepted Answer · answered Jul 05 '23 at 22:20

Since the table optimizes for performance, it will not automatically check for changes to the data array. Instead, when objects are added, removed, or moved on the data array, you can trigger an update to the table's rendered rows by calling its renderRows() method.

https://material.angular.io/components/table/overview

Calling renderRows() on Angular Material Table

Data is not rendered with mat-table [datasource] although it exists and is rendered with the "json" pipe

1 Answers1