Mat-Paginator not working on api based mat-table

Question

I'm implementing a mat-table that retrieve information from an API.

The mat-table is showing data as expected.

The mat-paginator is not working.

Below the code I'm using:

Component:

import {DataService} from '../../services/data.service';
import {Component, ViewChild, AfterViewInit, OnInit} from '@angular/core';
import {MatPaginator, MatTableDataSource} from '@angular/material';



@Component({
  selector: 'app-projects',
  templateUrl: './projects.component.html',
  styleUrls: ['./projects.component.css'],

})
export class ProjectsComponent implements OnInit,AfterViewInit {
  projects: any;
  dataSource = new MatTableDataSource();
  displayedColumns: any;
  length: number;
  pageSize: number=1;
  pageSizeOptions = [1, 5, 10, 50];
  @ViewChild(MatPaginator) paginator: MatPaginator;
  constructor(private dataService: DataService) { 

  }



  ngOnInit() {
    console.log("Retrieving projects");
    this.getProjects().then(
      projects => {
        console.log("Projects retrieved", projects);
        this.projects=projects;
        this.dataSource = this.projects;
        console.log(this.dataSource);
        this.displayedColumns = [
          'prj_id',
          'title',
          'priority_id'
        ];
        this.length=this.projects.length;


      }
    ).catch(function (data){
      console.log("Rejected", data);
    });

  }

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


  getProjects(){
    let promise = new Promise((resolve, reject) => {
      this.dataService.getProjects().subscribe(
        projects => {
          resolve(projects);
        },
        error => {
          console.log("error retrieving projects");
          reject("error retrieving projects");
        }
      )
    });
    return promise;
  }

}

export interface Projects {
  prj_id: string;
  title: string;
  priority_id: number;
}

HTML VIEW:

<div fxLayout="column" fxLayoutAlign="center center" >


    <button mat-raised-button color="primary" ><mat-icon>add</mat-icon>Project</button>

</div>
<div fxLayout="row" fxLayoutWrap="wrap">

  <div fxFlex.gt-sm="100" fxFlex.gt-xs="100" fxFlex="100">
      <mat-card>
          <mat-card-content> 
              <mat-card-title backgroundColor="primary">Projects</mat-card-title>
              <div class="table-rasponsive">
                  <mat-table #table [dataSource]="dataSource">

                  <!-- Position Column -->
                  <ng-container matColumnDef="prj_id">
                    <mat-header-cell *matHeaderCellDef> ID </mat-header-cell>
                    <mat-cell *matCellDef="let element"> {{element.prj_id}} </mat-cell>
                  </ng-container>

                  <!-- Name Column -->
                  <ng-container matColumnDef="title">
                    <mat-header-cell *matHeaderCellDef> TITLE </mat-header-cell>
                    <mat-cell *matCellDef="let element"> {{element.title}} </mat-cell>
                  </ng-container>

                   <!-- Name Column -->
                   <ng-container matColumnDef="priority_id">
                      <mat-header-cell *matHeaderCellDef> PRIORITY </mat-header-cell>
                      <mat-cell *matCellDef="let element"> {{element.priority_id}} </mat-cell>
                    </ng-container>



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

                <mat-paginator  #paginator
                                [length]="length"
                                [pageSize]="pageSize"
                                [pageSizeOptions]="pageSizeOptions">
                </mat-paginator>
              </div>    
          </mat-card-content>
      </mat-card>
  </div>
</div>

Answer 1

After having a lot of headaches I did figure out the problem. Check this line

this.dataSource = this.projects;

and change it with

this.dataSource.data = this.projects;

It should solve your problem. Also, ngAfterViewInit is ok, don't change it.