Nested FormGroups in FormArray not working

Question

I have a simple reactive form with a FormArray that will contain FromGroups.

I know this has been asked many times, but I can't still figure out why it's not working. I've tried many ways. This is are two simplified examples put together with what I've read from the docs and found online.

Component:

@Component({
  selector: 'app-professional-info-form',
  templateUrl: './professional-info-form.component.html',
  styleUrls: ['./professional-info-form.component.scss']
})
export class ProfessionalInfoFormComponent implements OnInit {

  protected professionalInfo: FormGroup;

  constructor() { }

  ngOnInit() {
    this.initForm();
  }

  private initForm() {
    this.professionalInfo = new FormGroup({
      trainings: new FormArray([
        new FormGroup({
          institutionId: new FormControl(null, null),
          title: new FormControl(null, null),
          description: new FormControl(null, null),
          institution: new FormControl(null, Validators.required),
          grade: new FormControl(null, null),
          from: new FormControl(null, Validators.required),
          to: new FormControl(null, null)
        })
      ])
    });
   
  }

}

HTML:

<form [formGroup]="professionalInfo" (ngSubmit)="onSubmit()" novalidate *ngIf="professionalInfo">
  <div formArrayName="trainings">
    <div *ngFor="let training of trainings.controls; index as t" [formGroupName]="t">
      <input type="text" [formControlName]="title" placeholder="Titolo" />
      <input type="text" [formControlName]="institution" placeholder="Istituto" />
      <input type="text" placeholder="Inizio" [formControlName]="from">
      <input type="text" placeholder="Fine" [formControlName]="to">
      <input type="text" placeholder="Voto" [formControlName]="grade" maxlength="5">
    </div>
  </div>
</form>

Console error:

ERROR TypeError: Cannot read property 'controls' of undefined
    at Object.eval [as updateDirectives] (ProfessionalInfoFormComponent.html:19)

If I add this method to the component:

get trainingsFormArray() {
    return (<FormArray>this.professionalInfo.get('trainings'));
  }

And edit the *ngFor like this:

<div *ngFor="let training of trainingsFormArray.controls; index as t" [formGroupName]="t">

The console error is:

ERROR Error: Cannot find control with path: 'trainings -> 0 -> '

Which is kind of crazy because if console.log 'trainingsFormArray' after initializing the form the output is the following:

console.log output

Every time I have to work with angular's reactive forms I encounter problems like this one. I can't seem to figure out a consistent way for making them work with dynamic controls like in this case. Please help me.

SiddAjmera · Accepted Answer · 2019-05-29 09:57:45Z

There's an issue in your template. Angular doesn't know what trainings is. Use professionalInfo.controls['trainings'].controls to have access to the controls in the trainings FormArray instead.

Something like this:

<form 
  [formGroup]="professionalInfo" 
  (ngSubmit)="onSubmit()" 
  novalidate 
  *ngIf="professionalInfo">
  <div formArrayName="trainings">
    <div 
      *ngFor="let training of professionalInfo.controls['trainings'].controls; index as t" 
      [formGroupName]="t">
      <input type="text" formControlName="title" placeholder="Titolo" />
      <input type="text" formControlName="institution" placeholder="Istituto" />
      <input type="text" placeholder="Inizio" formControlName="from">
      <input type="text" placeholder="Fine" formControlName="to">
      <input type="text" placeholder="Voto" formControlName="grade" maxlength="5">
    </div>
  </div>
</form>

Here's a Working Sample StackBlitz for your ref.

Sachin Gupta · Accepted Answer · 2019-05-29 10:05:01Z

1

You are using [formControlName]='title' , this would need the title to be a variable with the control name. You can get rid of the enclosing []and it would work fine. Use as:

formControlName='title'

answered May 29, 2019 at 10:05

Sachin Gupta

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