Angular: How to implement mat sorting in mat table with formarray

It's obvious that you got confused with the Angular Material table examples.

If you take a look on MatTable example with SortHeader you will notice that you can add your Sort child to your dataSource only if your dataSource is an instance of MatTableDataSource.

like: dataSource = new MatTableDataSource(ELEMENT_DATA);

@ViewChild(MatSort) sort: MatSort;

ngAfterViewInit() {
    this.dataSource.sort = this.sort;
}

This doesn't work in your case, since your albums which's your dataSource is a formArray, so you can solve it by using the matSortChange event that calls your custom method of sorting.

HTML:

<mat-table
    matSort
    [dataSource]="albums.controls"
    (matSortChange)="sortAlbums($event)">
        <!-- your columns here -->
</mat-table>

Typescript:

sortAlbums(sort: Sort) {
    var list: Album[] = this.albums.value;
    switch (sort.direction) {
      case 'desc':
        list = list.sort((a, b) => b.id - a.id);
        break;
      default:
        list = list.sort((a, b) => a.id - b.id);
        break;
    }
    this.albums.patchValue(list);
}