Angular Material editable table using FormArray

Question

I'm trying to build an inline editable table using the latest material+cdk for angular.

Question

How can I make mat-table use [formGroupName] so that the form fields can be referenced by its correct form path?

This is what I got so far: Complete StackBlitz example

Template

<form [formGroup]="form">
  <h1>Works</h1>
  <div formArrayName="dates" *ngFor="let date of rows.controls; let i = index;">
    <div [formGroupName]="i">
      <input type="date" formControlName="from" placeholder="From date">
      <input type="date" formControlName="to" placeholder="To date">
    </div>
  </div>


  <h1>Wont work</h1>
  <table mat-table [dataSource]="dataSource" formArrayName="dates">
    <!-- Row definitions -->
    <tr mat-header-row *matHeaderRowDef="displayColumns"></tr>
    <tr mat-row *matRowDef="let row; let i = index; columns: displayColumns;" [formGroupName]="i"></tr>

    <!-- Column definitions -->
    <ng-container matColumnDef="from">
      <th mat-header-cell *matHeaderCellDef> From </th>
      <td mat-cell *matCellDef="let row"> 
        <input type="date" formControlName="from" placeholder="From date">
      </td>
    </ng-container>

    <ng-container matColumnDef="to">
      <th mat-header-cell *matHeaderCellDef> To </th>
      <td mat-cell *matCellDef="let row">
        <input type="date" formControlName="to" placeholder="To date">
      </td>
    </ng-container>
  </table>
  <button type="button" (click)="addRow()">Add row</button>
</form>

Component

export class AppComponent implements  OnInit  {
  data: TableData[] = [ { from: new Date(), to: new Date() } ];
  dataSource = new BehaviorSubject<AbstractControl[]>([]);
  displayColumns = ['from', 'to'];
  rows: FormArray = this.fb.array([]);
  form: FormGroup = this.fb.group({ 'dates': this.rows });

  constructor(private fb: FormBuilder) { }

  ngOnInit() {
    this.data.forEach((d: TableData) => this.addRow(d, false));
    this.updateView();
  }

  emptyTable() {
    while (this.rows.length !== 0) {
      this.rows.removeAt(0);
    }
  }

  addRow(d?: TableData, noUpdate?: boolean) {
    const row = this.fb.group({
      'from'   : [d && d.from ? d.from : null, []],
      'to'     : [d && d.to   ? d.to   : null, []]
    });
    this.rows.push(row);
    if (!noUpdate) { this.updateView(); }
  }

  updateView() {
    this.dataSource.next(this.rows.controls);
  }
}

Problem

This wont work. Console yields

ERROR Error: Cannot find control with path: 'dates -> from'

It seems as if the [formGroupName]="i" has no effect, cause the path should be dates -> 0 -> from when using a formArray.

My current workaround: For this problem, I've bypassed the internal path lookup (formControlName="from") and use the form control directly: [formControl]="row.get('from')", but I would like to know how I can (or at least why I cannot) use the Reactive Form preferred way.

Any tips are welcome. Thank you.

---

Since I think this is a bug, I've registered an issue with the angular/material2 github repo.

Answer 1

Create a function that calculates the actual index.

getActualIndex(index : number)    {
    return index + pageSize * pageIndex;
}

You can get the pageSize and pageIndex from the paginator. Then, in the template use this function:

formControlName="getActualIndex(index)"

Answer 2

A little late to the party but I managed to get it working without relying on the index. This solution also supports filtering etc from the MatTableDataSource.

https://stackblitz.com/edit/angular-material-table-with-form-59imvq

Component

import {
  Component, ElementRef, OnInit
} from '@angular/core';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators'
import { AlbumService } from './album.service';
import { UserService } from './user.service';
import { Album } from './album.model';
import { User } from './user.model';
import { FormArray, FormGroup, FormBuilder } from '@angular/forms';
import { MatTableDataSource } from '@angular/material';

@Component({
  selector: 'table-form-app',
  templateUrl: 'app.component.html'
})
export class AppComponent implements OnInit {
  form: FormGroup;
  users: User[] = [];
  dataSource: MatTableDataSource<any>;
  displayedColumns = ['id', 'userId', 'title']
  constructor(
    private _albumService: AlbumService,
    private _userService: UserService,
    private _formBuilder: FormBuilder
    ) {}

  ngOnInit() {
    this.form = this._formBuilder.group({
      albums: this._formBuilder.array([])
    });
    this._albumService.getAllAsFormArray().subscribe(albums => {
      this.form.setControl('albums', albums);
      this.dataSource = new MatTableDataSource((this.form.get('albums') as FormArray).controls);
      this.dataSource.filterPredicate = (data: FormGroup, filter: string) => { 
          return Object.values(data.controls).some(x => x.value == filter); 
        };
    });
    this._userService.getAll().subscribe(users => {
      this.users = users;
    })
  }

  get albums(): FormArray {
    return this.form.get('albums') as FormArray;
  }

  // On user change I clear the title of that album 
  onUserChange(event, album: FormGroup) {
    const title = album.get('title');

    title.setValue(null);
    title.markAsUntouched();
    // Notice the ngIf at the title cell definition. The user with id 3 can't set the title of the albums
  }

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

HTML

<mat-form-field>
  <input matInput (keyup)="applyFilter($event.target.value)" placeholder="Filter">
</mat-form-field>

<form [formGroup]="form" autocomplete="off">
    <mat-table [dataSource]="dataSource">

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

      <!-- Id Column -->
      <ng-container matColumnDef="id">
        <mat-header-cell *matHeaderCellDef> Id </mat-header-cell>
        <mat-cell *matCellDef="let element"> {{element.get('id').value}}. </mat-cell>
      </ng-container>

      <!-- User Column -->
      <ng-container matColumnDef="userId">
        <mat-header-cell *matHeaderCellDef> User </mat-header-cell>
        <mat-cell *matCellDef="let element" [formGroup]="element">
          <mat-form-field floatLabel="never">
            <mat-select formControlName="userId" (selectionChange)="onUserChange($event, element)" required>
              <mat-option *ngFor="let user of users" [value]="user.id">
                {{ user.username }}
              </mat-option>
            </mat-select>
          </mat-form-field>
        </mat-cell>
      </ng-container>

      <!-- Title Column -->
      <ng-container matColumnDef="title">
        <mat-header-cell *matHeaderCellDef> Title </mat-header-cell>
        <mat-cell *matCellDef="let element;" [formGroup]="element">
          <mat-form-field floatLabel="never" *ngIf="element.get('userId').value !== 3">
            <input matInput placeholder="Title" formControlName="title" required>
          </mat-form-field>
        </mat-cell>
      </ng-container>

      <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
      <mat-row *matRowDef="let row; columns: displayedColumns;"></mat-row>
    </mat-table>
</form>
<mat-accordion>
  <mat-expansion-panel>
    <mat-expansion-panel-header>
      <mat-panel-title>
        Form value
      </mat-panel-title>
    </mat-expansion-panel-header>
    <code>
      {{form.value | json}}
    </code>
  </mat-expansion-panel>
</mat-accordion>

Answer 3

here is the sample code

In Html:

<form [formGroup]="tableForm">

<mat-table formArrayName="users" [dataSource]="dataSource">

  <ng-container cdkColumnDef="position">
    <mat-header-cell *cdkHeaderCellDef> No. </mat-header-cell>
    <mat-cell *cdkCellDef="let row let rowIndex = index"  [formGroupName]="rowIndex"> 
      <input type="text" size="2" formControlName="position"> </mat-cell>
  </ng-container>


  <ng-container cdkColumnDef="name">
    <mat-header-cell *cdkHeaderCellDef> Name </mat-header-cell>
    <mat-cell *cdkCellDef="let row let rowIndex = index"  [formGroupName]="rowIndex"> 
      <input type="text" size="7" formControlName="name">
    </mat-cell>
  </ng-container>

    <ng-container cdkColumnDef="weight">
    <mat-header-cell *cdkHeaderCellDef> Weight </mat-header-cell>
    <mat-cell *cdkCellDef="let row let rowIndex = index"  [formGroupName]="rowIndex"> 
      <input type="text" size="3" formControlName="weight">
    </mat-cell>
  </ng-container>

    <ng-container cdkColumnDef="symbol">
    <mat-header-cell *cdkHeaderCellDef> Symbol </mat-header-cell>
    <mat-cell *cdkCellDef="let row let rowIndex = index"  [formGroupName]="rowIndex"> 
      <input type="text" size="2" formControlName="symbol">
    </mat-cell>
  </ng-container>

  <!-- Header and Row Declarations -->
  <mat-header-row *cdkHeaderRowDef="displayedColumns"></mat-header-row>
  <mat-row *cdkRowDef="let row; columns: displayedColumns;"></mat-row>
</mat-table>
</form>

Controller code:

displayedColumns: string[] = ['position', 'name', 'weight', 'symbol'];


 dataSource ;
  tableForm: FormGroup;



 constructor(private formBuilder: FormBuilder){
 this.dataSource = [
  {position: 1, name: 'Hydrogen', weight: 1.0079, symbol: 'H'},
  {position: 2, name: 'Helium', weight: 4.0026, symbol: 'He'},
  {position: 3, name: 'Lithium', weight: 6.941, symbol: 'Li'},
  {position: 4, name: 'Beryllium', weight: 9.0122, symbol: 'Be'},
  {position: 5, name: 'Boron', weight: 10.811, symbol: 'B'},
  {position: 6, name: 'Carbon', weight: 12.0107, symbol: 'C'},
  {position: 7, name: 'Nitrogen', weight: 14.0067, symbol: 'N'},
  {position: 8, name: 'Oxygen', weight: 15.9994, symbol: 'O'},
  {position: 9, name: 'Fluorine', weight: 18.9984, symbol: 'F'},
  {position: 10, name: 'Neon', weight: 20.1797, symbol: 'Ne'},
];
  }

  ngOnInit(){
    this.tableForm= this.formBuilder.group({
        users: this.formBuilder.array([])
    })
    this.setUsersForm();
    this.tableForm.get('users').valueChanges.subscribe(users => {console.log('users', users)});
  }
  private setUsersForm(){
    const userCtrl = this.tableForm.get('users') as FormArray;
    this.dataSource.forEach((user)=>{
      userCtrl.push(this.setUsersFormArray(user))
    })
  };
  private setUsersFormArray(user){


    return this.formBuilder.group({
        position:[user.position],
        name:[user.name],
        weight:[user.weight], 
        symbol:[user.symbol]
    });
  }

Answer 4

I would use the index which we can get within matCellDef binding:

*matCellDef="let row; let index = index" [formGroupName]="index"

Forked Stackblitz