Use FontAwesome icons in table header in Angular

Question

I'm trying to set the sort, sortUp, and sortDown icons to my table headers, following the table tutorial from ng-bootstrap.

There's a NgbdSortableHeader directive that changes the sorting of the column:

@Directive({
  selector: 'th[sortable]',
  host: {
    '[class.asc]': 'direction === "asc"',
    '[class.desc]': 'direction === "desc"',
    '(click)': 'rotate()'
  }
})
export class NgbdSortableHeader {
  @Input() sortable: string = '';
  @Input() direction: SortDirection = '';
  @Output() sort = new EventEmitter<SortEvent>();

  rotate() {
    this.direction = rotate[this.direction];
    this.sort.emit({column: this.sortable, direction: this.direction});
  }
}

And the component that has the table:

@Component({
  selector: 'app-users',
  templateUrl: './users.component.html',
  styleUrls: ['./users.component.scss'],
  providers: [UserService]
})
export class UsersComponent implements OnInit {
  faSort = faSort;
  faSortUp = faSortUp;
  faSortDown = faSortDown;

  users$: Observable<User[]>;
  total$: Observable<number>;

  @ViewChildren(NgbdSortableHeader) headers!: QueryList<NgbdSortableHeader>;

  constructor() {
  }

  ngOnInit(): void {
  }

  onSort({column, direction}: SortEvent) {
    // resetting other headers
    this.headers.forEach(header => {
      if (header.sortable !== column) {
        header.direction = '';
      }
    });


    this.service.sortColumn = column;
    this.service.sortDirection = direction;
  }
}

I wonder if there's a way to access the current column sorting order and replace the icon from the item or hide them.

<th scope="col" sortable="firstName" (sort)="onSort($event)">
  Name
  <fa-icon [icon]="faSort"></fa-icon>
  <fa-icon [icon]="faSortUp"></fa-icon>
  <fa-icon [icon]="faSortDown"></fa-icon>
</th>

Answer 1

I was able to solve my issue by using @ChildComponent in the sort directive:

<th scope="col" sortable="firstName" (sort)="onSort($event)">
  Name
  <fa-icon [icon]="faSort" size="lg"></fa-icon>
</th>

import { Directive, EventEmitter, Input, Output, ViewChild, ContentChild, ElementRef } from "@angular/core";
import { FaIconComponent } from "@fortawesome/angular-fontawesome";
import { faSort, faSortUp, faSortDown } from "@fortawesome/pro-regular-svg-icons";

export type SortDirection = 'asc' | 'desc' | '';
const rotate: {[key: string]: SortDirection} = { 'asc': 'desc', 'desc': '', '': 'asc' };

export interface SortEvent {
  column: string;
  direction: SortDirection;
}

@Directive({
  selector: 'th[sortable]',
  host: {
    '[class.asc]': 'direction === "asc"',
    '[class.desc]': 'direction === "desc"',
    '(click)': 'rotate()'
  }
})
export class NgbdSortableHeader {
  @Input() sortable: string = '';
  @Input() direction: SortDirection = '';
  @Output() sort = new EventEmitter<SortEvent>();

  @ContentChild(FaIconComponent) sortIcon?: FaIconComponent;

  rotate() {
    this.direction = rotate[this.direction];
    this.sort.emit({column: this.sortable, direction: this.direction});

    if (this.sortIcon !== undefined)
    {
        this.sortIcon.icon = this.direction === 'asc' ? faSortDown : this.direction === 'desc' ? faSortUp : faSort;
        this.sortIcon.render();
    }
  }
}