Why I can't get result from parent component in Angular

Question

I want child components in angular to separate Material Table(child) from other elements(parent), but the weird thing is that it seems I cannot get data from the parent or I get initialized data from parents and cannot refresh. Here is the Code: firstly, the parent .ts file:

@Component({
  selector: 'app-dashboard',
  templateUrl: './dashboard.component.html',
  styleUrls: ['./dashboard.component.scss']
})
export class DashboardComponent implements OnInit{

  ticketList: Ticket[] = [];
  originalTicketList: Ticket[] = [];
  filterAllForm: FormGroup;
  labelList: string[];
  homeLabelList: string[];
  currentTicketId: string;
  searchBy: string = '';
  maxall : number = 100;
  isLoading :boolean = true;
  showRelatedTickets = true;

  constructor(private ticket: TicketService,
    private formBuilder: FormBuilder) { }

  ngOnInit() {
    this.filterAllForm = this.formBuilder.group({
      startDate: [''],
      endDate: ['']
    });
    this.getAllTicket();

  }


  get filterFormControls() { return this.filterAllForm.controls; }



  getAllTicket() {
    let queryParams = '';
    console.log(this.currentTicketId) + " " + this.searchBy;
    if (this.searchBy === 'id') {
      queryParams = 'id=' + this.currentTicketId;
      this.showRelatedTickets = true;
    }else if(this.searchBy !== ''){
      queryParams = this.searchBy + '=' + this.currentTicketId;
      this.showRelatedTickets = false;
    }

    this.ticket.getAllTicket(queryParams).then((res: Ticket[]) => {
      this.isLoading = false;
      this.ticketList = res;
      this.originalTicketList = this.ticketList;
    });
  }


  searchTicket() {
    this.isLoading = true;
    this.getAllTicket();
  }

}

the parent html like this:

    <div class="ticket-container">
      <mat-card *ngIf="isLoading" class="mat-card-style">
        <mat-progress-spinner color="primary" mode="indeterminate">
        </mat-progress-spinner>
      </mat-card>
      <div *ngIf="showRelatedTickets">
        <app-dashboard-related-tickets-table [tablesource]="ticketList">
        </app-dashboard-related-tickets-table>
      </div>
      <div *ngIf="!showRelatedTickets">
        <app-dashboard-non-related-tickets-table [tablesource]="ticketList">
        </app-dashboard-non-related-tickets-table>
      </div>
    </div>

and there are two children you can see, one is app-dashboard-related-tickets-table and another one is app-dashboard-non-related-tickets-table, they have a different format and changed by the button showRelatedTickets . Here I will show the first one the child(app-dashboard-related-tickets-table) .ts file:

@Component({
  selector: 'app-dashboard-related-tickets-table',
  templateUrl: './dashboard-related-tickets-table.component.html',
  styleUrls: ['./dashboard-related-tickets-table.component.scss']
})
export class DashboardRelatedTicketsTableComponent implements OnInit, AfterViewInit{
  dataSource: any;
  displayedDetailColumns = ['id', 'caseStatus', 'anchorPoint', 'findingSourceSystem','caseCreateTimestamp', 'resolvedBy', 'resolution', 'resolutionNote'];
  maxall: number = 100;

  @Input() tablesource: Ticket[];
  @ViewChild(MatPaginator, {static: false}) paginator: MatPaginator;
  @ViewChild(MatSort, { static: true }) sort: MatSort;

  applyFilter(filterValue: string) {
    this.dataSource.filter = filterValue.trim().toLowerCase();

  }
  constructor() { }

  ngOnInit() {
    console.log(this.tablesource);
    this.dataSource = new MatTableDataSource(this.tablesource);
  }

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

  getPageSizeOptions(): number[] {
    if (this.dataSource.data.length>this.maxall){
      return [20, 50, this.dataSource.data.length];
    }else{
      return [20, 50, this.maxall];
    }
  }

}

then the child(app-dashboard-related-tickets-table) .html file:

<table mat-table matTableExporter [dataSource]="dataSource" matSort class="mat-elevation-z8"
    #exporter="matTableExporter">
    <!-- Ticket Column -->
    <ng-container matColumnDef="id">
        <th mat-header-cell *matHeaderCellDef mat-sort-header class="mat-column-id-source"> SIR ID </th>
        <td mat-cell *matCellDef="let element" class="mat-column-id-source">
            <a href='ticket/{{element.id}}'>{{element.id}}</a>
        </td>
    </ng-container>

    <!-- Type Column event source -->
    <ng-container matColumnDef="findingSourceSystem">
        <th mat-header-cell *matHeaderCellDef mat-sort-header class="mat-column-id-source"> Source </th>
        <td mat-cell *matCellDef="let element" class="mat-column-id-source"> {{element.findingSourceSystem}} </td>
    </ng-container>

    <!-- Type Column Related Event count -->
    <ng-container matColumnDef="anchorPoint">
        <th mat-header-cell *matHeaderCellDef class="mat-column-related-ticket-num"> Related Cases </th>
        <td mat-cell *matCellDef="let element" class="mat-column-related-ticket-num">
            {{element.relatedVertices}} </td>
    </ng-container>

    <!-- Type Column event source -->
    <ng-container matColumnDef="caseStatus">
        <th mat-header-cell *matHeaderCellDef mat-sort-header class="mat-column-case"> Case Status </th>
        <td mat-cell *matCellDef="let element" class="mat-column-case"> {{element.caseStatus}} </td>
    </ng-container>

    <!-- Type Column event source -->
    <ng-container matColumnDef="caseCreateTimestamp">
        <th mat-header-cell *matHeaderCellDef mat-sort-header class="mat-column-date"> Case Created </th>
        <td mat-cell *matCellDef="let element" class="mat-column-date">
            {{element.caseCreateTimestamp | date:'MMM d, y, h:mm:ss a'}}
        </td>
    </ng-container>

    <ng-container matColumnDef="resolvedBy">
        <th mat-header-cell *matHeaderCellDef class="mat-column-resolvedBy"> Resolved By </th>
        <td mat-cell *matCellDef="let element" class="mat-column-resolvedBy"> {{element.resolvedBy}}
        </td>
    </ng-container>

    <ng-container matColumnDef="resolution">
        <th mat-header-cell *matHeaderCellDef class="mat-column-closeCode"> Close Code </th>
        <td mat-cell *matCellDef="let element" class="mat-column-closeCode"> {{element.resolution}}
        </td>
    </ng-container>

    <ng-container matColumnDef="resolutionNote">
        <th mat-header-cell *matHeaderCellDef class="mat-column-closeNote"> Close Note </th>
        <td mat-cell *matCellDef="let element" class="mat-column-closeNote"> {{element.resolutionNote}}
        </td>
    </ng-container>
    <tr mat-header-row *matHeaderRowDef="displayedColumns; sticky: true"></tr>
    <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
</table>
<mat-paginator [pageSizeOptions]="getPageSizeOptions()" showFirstLastButtons></mat-paginator>
<button mat-raised-button (click)="exporter.exportTable('csv')" class="export-button">Export Results</button>

So in the child component, I use @input tablesource, and display dataSource. but the result is like this:

The child component seems loaded because the export result button is already there, but the table didn't show. I just to do

console.log(tablesource)

I got []

This is the browser console log: Any Idea what happened?

I was trying to reproduce here: https://stackblitz.com/edit/angular-hbzpvr but I am sorry, I am not good at angular, so I am not sure how to load parent to page.

Answer 1

According to your console output, you use tablesource in your child component before it has been updated by the parent component. Instead of creating datasource in ngOnInit of the child component, define the tablesource property as a setter and create datasource in that setter:

@Input() set tablesource(value: Ticket[]) {
  console.log(value);
  this.dataSource = new MatTableDataSource(value);
}

See this stackblitz for a demo.