Angular Material Table: Sorting not working

Question

In my Angular app (using Angular Material) I have several tables.

The strange thing is that, in one case, sorting works, while, in another case, it doesn't.

Here is the table that works:

<table mat-table [dataSource]="dataSource" matSort>

  <ng-container matColumnDef="id">
    <th mat-header-cell *matHeaderCellDef> ID </th>
    <td mat-cell *matCellDef="let row"> {{row.id}} </td>
  </ng-container>

  <ng-container matColumnDef="firstName">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> First Name </th>
    <td mat-cell *matCellDef="let row"> {{row.firstName}} </td>
  </ng-container>

  <ng-container matColumnDef="lastName">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Last Name </th>
    <td mat-cell *matCellDef="let row"> {{row.lastName}} </td>
  </ng-container>

  <ng-container matColumnDef="viewProfile">
    <th mat-header-cell *matHeaderCellDef class="viewProfile"> Profile </th>
    <td mat-cell *matCellDef="let row" class="viewProfile">
      <button mat-icon-button (click)="openProfile(row.id)">
                <mat-icon aria-label="icon-button with a page-view icon">pageview</mat-icon>
              </button>
    </td>
  </ng-container>

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

</table>

... and here is the table that doesn't work:

<table class="table2" mat-table [dataSource]="dataSource2" matSort>

  <ng-container matColumnDef="name">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Project </th>
    <td mat-cell *matCellDef="let row"> {{row.name}} </td>
  </ng-container>
  <ng-container matColumnDef="role">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Role </th>
    <td mat-cell *matCellDef="let row"> {{row.role}} </td>
  </ng-container>
  <ng-container matColumnDef="beginning">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> Beginning </th>
    <td mat-cell *matCellDef="let row"> {{row.beginning | date : "mediumDate"}} </td>
  </ng-container>
  <ng-container matColumnDef="end">
    <th mat-header-cell *matHeaderCellDef mat-sort-header> End </th>
    <td mat-cell *matCellDef="let row"> {{row.end | date : "mediumDate"}} </td>
  </ng-container>

  <tr mat-header-row *matHeaderRowDef="displayedColumns2"></tr>
  <tr mat-row *matRowDef="let row; columns: displayedColumns2;"></tr>
</table>

As you can see, in both cases I use "matSort" (in the table tag) and "mat-sort-header" (for the columns that are supposed to be sortable).

Furthermore, in each case I do the same import in the component.ts file:

import { MatTableDataSource, MatPaginator, MatSort, MatDialog } from '@angular/material';

I just don't get why sorting works in the first case but not in the second. Does anybody have any ideas what's going on here?

Answer 1

Make sure that the column_name in the displayedColumns array,

displayedColumns = ['column_name'];

the html container,

ng-container matColumnDef="column_name"

and the keys of the dataSource objects,

dataSource = [ {"column_name": "value"} ];

ALL MATCH PERFECTLY.

This can also be the reason that a specific set of data doesn't work and others do.

Answer 2

Are you sure your second table ( the one where sort is not working ) is not wrapped in a div with *ngIf ? Because that is a common problem, as when the template is rendered, because of the *ngIf, matSort is undefined. Here is how to fix it : Angular 5 Material Data Table sorting not working