How to group several checkboxes with angular-material

Question

Let's say I have a form to create a store. I want to input its name, and the days the store will be open.

So I'll have a form, with some inputs, and I want to group checkboxes in one mat-form-field.

store-form-component.html :

<form (ngSubmit)="onSaveStore()" [formGroup]="storeForm">
  <mat-form-field>
    <mat-label>Store name</mat-label>
    <input matInput placeholder="store name" formControlName="name" required>
  </mat-form-field>
  <mat-form-field [formGroup]="storeForm.controls.availableDays>
    <mat-checkbox *ngFor="let availableDay of storeForm.controls.availableDays.controls; let i=index" formControlName="{{i}}">{{i}}</mat-checkbox>
  </mat-form-field >
</form>

store-form-component.ts :

export class StoreFormComponent implements OnInit {

  // Form Groups
  storeForm: FormGroup;

  constructor(
    private formBuilder: FormBuilder
  ) {}

  ngOnInit(): void { 
    this.initForm();
  }

  initForm(): void {
    this.storeForm = this.formBuilder.group({
      name: "",
      availableDays: this.getAvailableDays()
    });
  }

  getAvailableDays(): FormGroup {
    return this.formBuilder.group({
      monday: false,
      tuesday: false,
      wednesday: false,
      thursday: false,
      friday: false,
      saturday: false,
      sunday: false
    });
  }

It does not work and I can't figure why...

edit : thanks to @g-tranter (and others SO posts), I could fix the issue. The final code looks like :

store-form-component.html :

<form (ngSubmit)="onSaveStore()" [formGroup]="storeForm">
  <div [formGroup]="storeForm.controls.availableDays">
    <mat-checkbox *ngFor="let availableDay of days;" formControlName="{{availableDay}}">{{availableDay}}</mat-checkbox>
  </div>
</form>

store-form-component.ts :

export class StoreComponent implements OnInit {
  // Form Groups
  storeForm: FormGroup;
  days: Array<string>;

  constructor(private formBuilder: FormBuilder) {}

  ngOnInit(): void {
    this.initForm();

    // this is useful to iterate over the form group
    this.days = Object.keys(this.storeForm.controls.availableDays.value);
  }

  initForm(): void {
    this.storeForm = this.formBuilder.group({
      name: "",
      availableDays: this.getAvailableDays()
    });
  }

  getAvailableDays(): FormGroup {
    return this.formBuilder.group({
      monday: false,
      tuesday: false,
      wednesday: false,
      thursday: false,
      friday: false,
      saturday: false,
      sunday: false
    });
  }
}

Answer 1

Maybe you need a mat-selection-list

Check Angular Material documentation

Hope it helps you!

Answer 2

You are setting the form control name to a numeric index:

formControlName="{{i}}"

which doesn't exist in the form group.

You need to set it to "monday" etc. or set

[formControl]="availableDay"