Angular + Material - How to refresh a data source (mat-table)

Question

I am using a mat-table to list the content of the users chosen languages. They can also add new languages using dialog panel. After they added a language and returned back.

Answer 1

Trigger a change detection by using ChangeDetectorRef in the refresh() method just after receiving the new data, inject ChangeDetectorRef in the constructor and use detectChanges like this:

import { Component, OnInit, ChangeDetectorRef } from '@angular/core';
import { LanguageModel, LANGUAGE_DATA } from '../../../../models/language.model';
import { LanguageAddComponent } from './language-add/language-add.component';
import { AuthService } from '../../../../services/auth.service';
import { LanguageDataSource } from './language-data-source';
import { LevelbarComponent } from '../../../../directives/levelbar/levelbar.component';
import { DataSource } from '@angular/cdk/collections';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';
import { MatSnackBar, MatDialog } from '@angular/material';

@Component({
  selector: 'app-language',
  templateUrl: './language.component.html',
  styleUrls: ['./language.component.scss']
})
export class LanguageComponent implements OnInit {
  displayedColumns = ['name', 'native', 'code', 'level'];
  teachDS: any;

  user: any;

  constructor(private authService: AuthService, private dialog: MatDialog,
              private changeDetectorRefs: ChangeDetectorRef) { }

  ngOnInit() {
    this.refresh();
  }

  add() {
    this.dialog.open(LanguageAddComponent, {
      data: { user: this.user },
    }).afterClosed().subscribe(result => {
      this.refresh();
    });
  }

  refresh() {
    this.authService.getAuthenticatedUser().subscribe((res) => {
      this.user = res;
      this.teachDS = new LanguageDataSource(this.user.profile.languages.teach);
      this.changeDetectorRefs.detectChanges();
    });
  }
}

Answer 2

this.dataSource = new MatTableDataSource<Element>(this.elements);

Add this line below your action of add or delete the particular row.

refresh() {
  this.authService.getAuthenticatedUser().subscribe((res) => {
    this.user = new MatTableDataSource<Element>(res);   
  });
}

Answer 3

In Angular 9, the secret is this.dataSource.data = this.dataSource.data;

Example:

import { MatTableDataSource } from '@angular/material/table';

dataSource: MatTableDataSource<MyObject>;

refresh(): void {
    this.applySomeModif();
    // Do what you want with dataSource

    this.dataSource.data = this.dataSource.data;
}

applySomeModif(): void {
    // add some data
    this.dataSource.data.push(new MyObject());
    // delete index number 4
    this.dataSource.data.splice(4, 0);
}

Answer 4

in my case (Angular 6+), I inherited from MatTableDataSource to create MyDataSource. Without calling after this.data = someArray

this.entitiesSubject.next(this.data as T[])

data where not displayed

class MyDataSource

export class MyDataSource<T extends WhateverYouWant> extends MatTableDataSource<T> {

    private entitiesSubject = new BehaviorSubject<T[]>([]);


    loadDataSourceData(someArray: T[]){
        this.data = someArray //whenever it comes from an API asyncronously or not
        this.entitiesSubject.next(this.data as T[])// Otherwise data not displayed
    }

    public connect(): BehaviorSubject<T[]> {
        return this.entitiesSubject
    }

}//end Class 

Answer 5

I think the MatTableDataSource object is some way linked with the data array that you pass to MatTableDataSource constructor.

For instance:

dataTable: string[];
tableDS: MatTableDataSource<string>;

ngOnInit(){
   // here your pass dataTable to the dataSource
   this.tableDS = new MatTableDataSource(this.dataTable); 
}

So, when you have to change data; change on the original list dataTable and then reflect the change on the table by call _updateChangeSubscription() method on tableDS.

For instance:

this.dataTable.push('testing');
this.tableDS._updateChangeSubscription();

That's work with me through Angular 6.