Angular Material + GAPI: table shows rows, but with empty cells

Question

I'm integrating angular material and Google api. I want to show in a table the response of the api. The problem is that the mat-cell of the rows of the mat-table are not populated, but the row is showned. This is my table:

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

    <ng-container matColumnDef="name">
      <mat-header-cell *matHeaderCellDef> Name </mat-header-cell>
      <mat-cell *matCellDef="let user"> {{user.name}} </mat-cell>
    </ng-container>
    <ng-container matColumnDef="age">
      <mat-header-cell *matHeaderCellDef> Age </mat-header-cell>
      <mat-cell *matCellDef="let user"> {{user.age}} </mat-cell>
    </ng-container>
    <ng-container matColumnDef="city">
      <mat-header-cell *matHeaderCellDef> City </mat-header-cell>
      <mat-cell *matCellDef="let user"> {{user.city}} </mat-cell>
    </ng-container>
    <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
    <mat-row *matRowDef="let row; columns: displayedColumns;"></mat-row>
  </mat-table>

This is an interface that I have created:

    export interface User { name: string; age: number; city: string; }

This is the component associated with the table:

    export class UsertableComponent implements OnInit, OnChanges {
  @Input() apiReady: boolean;

  dataSource: UserDataSource;
  displayedColumns = ['name', 'age', 'city'];

  constructor(private userService: UserService) {

  }

  ngOnInit() {

  }

  ngOnChanges(changes: SimpleChanges) {
    if (this.apiReady) {
      this.dataSource = new UserDataSource(this.userService);
    }
  }
}

export class UserDataSource extends DataSource<any> {
  constructor(private userService: UserService) {
    super();
  }

  connect(): Observable<User[]> {
    return this.userService.getUsers();
  }

  disconnect() {

  }
}

And here, finally, the nightmare. The service that calls the gapi and return the data. I can ensure that the api respond and in particular this line of code response.result.users[0].name.fullName correspond to a string object with a value.

export class UserService {
  private serviceUrl = environment.apiUrl + '/getcust/';
  private apiLoaded = false;
  constructor(private http: HttpClient) { }

  getUsers(): Observable<User[]> {
    /* // THIS WORKS!!!
        const u: User = {
          'name': 'ss',
          'city': 'città',
          'age': 3
        };
        return Observable.create(observable => {
          observable.next([u]);
          observable.complete();
        });
     */

    return Observable.create(observable => { // THIS DOESN'T WORK
      return gapi.client.directory.users.list({
        'customer': 'my_customer',
        'maxResults': 1,
        'orderBy': 'email'
      }).then(response => {

        const u: User = {
          'name': response.result.users[0].name.fullName,
          'city': 'citta',
          'age': 3
        };

        observable.next([u]);
        observable.complete();
      });
    });
  }
}

As you see in the comment, the commented lines works, the others does not.

Result with empty cells

Result with populated cells, without calling GAPI

Answer 1

The solution is:

Import this:

import {ChangeDetectorRef} from '@angular/core';

The constructor of the component:

constructor(private cd: ChangeDetectorRef) {
  }

In the ngInit initialize the datasource:

    ngOnInit() {
    this.dataSource = new UserDataSource();
}

Use BehaviorSubject (and the method asObservable) to change the content of the datasource at any time, but when the data changes in the table don't forget to call:

this.cd.detectChanges();

to update cells content