Angular Material MatTableDataSource with Firestore

Question

I currently have a data table populated with data received from Firestore. I also used MatTableDataSource to implement pagination, sorting and filtering. All 3 are working fine, but for some reason my data is only loaded once when the page refreshes. If I go to another page and then return to the table, the data will disappear. I am at a loss why this is happening. Below is my code.

Service

import { Injectable } from '@angular/core';
import { AngularFirestore, AngularFirestoreCollection, AngularFirestoreDocument } from 'angularfire2/firestore';
import { Account } from './../models/account.model';
import { Observable } from 'rxjs/Observable';

@Injectable()
export class AccountService {
  accountsCollection: AngularFirestoreCollection<Account>;
  accounts: Observable<Account[]>;

  constructor(public afs: AngularFirestore) {
    this.accountsCollection = afs.collection('accounts');

    this.accounts = this.accountsCollection.snapshotChanges().map(changes => {
      return changes.map(a => {
        const data = a.payload.doc.data() as Account;
        data.id = a.payload.doc.id;
        return data;
      });
    });

  }

  getAccounts() {
    return this.accounts;
  }

}

Component

import { Account } from './../../../models/account.model';
import { Component, ViewChild, OnInit } from '@angular/core';
import { MatPaginator, MatSort, MatTableDataSource } from '@angular/material';
import { AccountService } from '../../../services/account.service';
import { AfterViewInit } from '@angular/core/src/metadata/lifecycle_hooks';

@Component({
  selector: 'app-account-table',
  templateUrl: './account-table.component.html',
  styleUrls: ['./account-table.component.css']
})
export class AccountTableComponent implements AfterViewInit {
  dataSource = new MatTableDataSource<Account>();
  displayedColumns = [
    'salesStep',
    'status',
    'idn',
    'hospital',
    'state',
    'regionalManager',
    'accountExecutive',
    'clientLiaison',
    'gpo'
  ];

  @ViewChild(MatPaginator) paginator: MatPaginator;
  @ViewChild(MatSort) sort: MatSort;

  constructor(private accountService: AccountService) {}

  ngAfterViewInit() {
    this.accountService.getAccounts().subscribe(data => {
      this.dataSource.data = data;
      console.log(this.dataSource.data);
    });
    this.dataSource.paginator = this.paginator;
    this.dataSource.sort = this.sort;
  }

  applyFilter(filterValue: string) {
    filterValue = filterValue.trim(); // Remove whitespace
    filterValue = filterValue.toLowerCase(); // Datasource defaults to lowercase matches
    this.dataSource.filter = filterValue;
  }

}

HTML

<div class="example-header">
  <mat-form-field>
    <input matInput #filter (keyup)="applyFilter($event.target.value)" placeholder="Search">
  </mat-form-field>
</div>

<mat-card class="example-container">

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

    <!--- Note that these columns can be defined in any order.
          The actual rendered columns are set as a property on the row definition" -->

    <!-- Sales Step Column -->
    <ng-container matColumnDef="salesStep">
      <mat-header-cell *matHeaderCellDef mat-sort-header> Sales Step </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.salesStep}} </mat-cell>
    </ng-container>

    <!-- Status Column -->
    <ng-container matColumnDef="status">
      <mat-header-cell *matHeaderCellDef mat-sort-header> Status </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.status}} </mat-cell>
    </ng-container>

    <!-- IDN Column -->
    <ng-container matColumnDef="idn">
      <mat-header-cell *matHeaderCellDef mat-sort-header> IDN </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.idn}} </mat-cell>
    </ng-container>

    <!-- Hospital Column -->
    <ng-container matColumnDef="hospital">
      <mat-header-cell *matHeaderCellDef mat-sort-header> Hospital </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.hospital}} </mat-cell>
    </ng-container>

    <!-- State Column -->
    <ng-container matColumnDef="state">
      <mat-header-cell *matHeaderCellDef mat-sort-header> State </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.state}} </mat-cell>
    </ng-container>

    <!-- Regional Manager Column -->
    <ng-container matColumnDef="regionalManager">
      <mat-header-cell *matHeaderCellDef mat-sort-header> RM </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.regionalManager}} </mat-cell>
    </ng-container>

    <!-- Account Executive Column -->
    <ng-container matColumnDef="accountExecutive">
      <mat-header-cell *matHeaderCellDef mat-sort-header> AE </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.accountExecutive}} </mat-cell>
    </ng-container>

    <!-- Client Liaison Column -->
    <ng-container matColumnDef="clientLiaison">
      <mat-header-cell *matHeaderCellDef mat-sort-header> CL </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.clientLiaison}} </mat-cell>
    </ng-container>

    <!-- GPO Column -->
    <ng-container matColumnDef="gpo">
      <mat-header-cell *matHeaderCellDef mat-sort-header> GPO </mat-header-cell>
      <mat-cell *matCellDef="let row"> {{row.gpo}} </mat-cell>
    </ng-container>



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

  <!-- <div class="example-no-results"
       [style.display]="(accountService.accounts | async)?.length">
    No accounts found matching filter.
  </div> -->

  <mat-paginator #paginator
                [pageSize]="10"
                [pageSizeOptions]="[5, 10, 20]">
  </mat-paginator>
</mat-card>

Answer 1

This might work better for the getAccounts method:

  getAccountsX() {
    return this.afs.collection<Account[]>('accounts').snapshotChanges().map((accounts) => {
      return accounts.map(a => {
        const data = a.payload.doc.data() as Account;
        const id = a.payload.doc.id;
        return { id, ...data }
      });
    });
  }

firestore , , ngOnInit .

, accounts: Observable<Account[]>, Observable<Account[]> getAccountsX(). * ngIf , : *ngIf="(accounts | async) as acts". dataSource acts. DataTable, , , . , .

:

:

, , , Observable, , , :

  accountsObservable: Observable<Account[]>;
  accountsArray: Account[];

  constructor(
    private ds: DatabaseService
  ) {}

  ngOnInit() {
    this.accountsObservable = this.ds.getAccountsX();

    this.accountsObservable.subscribe(accounts => {
      this.accountsArray = accounts;
    });
  }

, , , * ngFor ASYNC-, , :

<!-- This div below is subscribing to the Observable in markup using the 'async' pipe to make sure it waits for data -->
<div id="markup-subscription" *ngFor="let act of (accountsObservable | async)">
  <p>{{ act?.id }}</p>
</div>

<!-- This div below is looping through the array that was pulled from the subscription of the Observable -->
<div id="component-subscription" *ngFor="let act of accountsArray">
  <p>{{ act?.id }}</p>
</div>

, . , , , * ngFor , DOM. *ngIf accountArray, , :

<div id="component-subscription" *ngIf="accountsArray" *ngFor="let act of accountsArray">

, MatDataTable, , ,

, , , Observable ​​:

    const subscription = this.accountsObservable.subscribe(accounts => {
      this.accountsArray = accounts;
    });

    subscription.unsubscribe();

, , .

Answer 2

, getAccounts(). unsubscribe() ngOnDestroy. , , af2 , . .

Answer 3

. .

constructor(public afs: AngularFirestore) {
    this.accountsCollection = afs.collection('accounts');
}

getAccounts() {
    return this.accounts = this.accountsCollection.snapshotChanges().map(changes => {
      return changes.map(a => {
        const data = a.payload.doc.data() as Account;
        data.id = a.payload.doc.id;
        return data;
      });
    });
  }

, .