How to use the MatTableDataSource with an observable?

Question

I am using the mat-table and I am trying to use the MatTableDataSource with an observable (I get the data from a web service), but I don't know how to configure the MatTableDataSource to use an observable instead of an array.

Is the only solution to this problem, to subscribe to the observable in the ngOnInit method and always create a new MatTableDataSource when new data arrives?

This is what I have until now, but I don't know if this is the correct solution for working with the MatTableDataSource with an observable.

dataSource: MatTableDataSource<Thing>;
@ViewChild(MatPaginator, { static: true }) paginator: MatPaginator;
@ViewChild(MatSort, { static: true }) sort: MatSort;

ngOnInit() {
    getThings().subscribe(things => {
        this.dataSource = new MatTableDataSource(things);
        this.dataSource.paginator = this.paginator;
        this.dataSource.sort = this.sort;
        });
}

Answer 1

You should be able to new up the MatTableDataSource once at the class level and then use the data setter in ngOnInit.

dataSource = new MatTableDataSource<Thing>();
@ViewChild(MatPaginator, { static: true }) paginator: MatPaginator;
@ViewChild(MatSort, { static: true }) sort: MatSort;

ngOnInit() {
    getThings().subscribe(things => {
        this.dataSource.data = things;
        this.dataSource.paginator = this.paginator;
        this.dataSource.sort = this.sort;
    });
}

Answer 2

I've released a library for that: @matheo/datasource

I explain the basic concepts in this article:
https://medium.com/@matheo/reactive-datasource-for-angular-1d869b0155f6

and in the example code, you can see how I fetch items from a Firebase database and manipulate the pagination. sorting and filters in the example repo
I hope that you like it and give me your opinion about it ;)

Answer 3

this is a workaround, because MatTableDataSource doesn't support Observable as data source

import { MatTableDataSource } from '@angular/material';
import { Observable, Subscription } from 'rxjs';
import { SomeInterface} from './some.interface';

export class CustomDataSource extends MatTableDataSource<SomeInterface> {

    private collection: SomeInterface[] = [];

    private collection$: Subscription;

    constructor(collection: Observable<SomeInterface[]>) {
        super();
        this.collection$ = collection.subscribe(data => {
           this.data = data; // here you have to adjust the behavior as needed
        });
    }

   disconnect() {
     this.collection$.unsubscribe();
     super.disconnect();
   }
}

then in component:

dataSource: CustomDataSource;

ngOnInit(): void {
  const observableData$ = getData();
  this.dataSource = new CustomDataSource(observableData$);
  // this.dataSource.sort = this.sort; // add sorting or filter
}

example: stackblitz

Answer 4

You can use an observable too, just (*)

[dataSource]="dataSource|async"

(*) really you needn't use the pipe async

See an example in stackblitz, where I replace the first example of the doc by

dataSource = of(ELEMENT_DATA).pipe(delay(1000));