Angular2 reactive form containing a list

Question

I am attempting to create a form for a user that will allow one to may phone numbers to be associated with the user. Is this possible with the current implementation of reactive forms? For example, I would want the below form to accept potentially many phone numbers. My front end implementation would show the phone number field, and would have a button that would allow for an additional phone number field to be added.

userForm = new FormGroup({
  firstName: new FormControl('', Validators.required),
  lastName: new FormControl('', Validators.required),
  phoneNumber: new FormControl('', Validators.required)
});

My hack solution would be

userForm = new FormGroup({
  firstName: new FormControl('', Validators.required),
  lastName: new FormControl('', Validators.required),
  phoneNumber: new FormControl('', Validators.required),
  phoneNumber1: new FormControl(),
  phoneNumber2: new FormControl(),
  phoneNumber3: new FormControl(),
  phoneNumber4: new FormControl()
});

I could suppress the additional phone fields until the add an additional phone number button is clicked.

Answer 1

What you want to use is a FormArray where you can add new Form Controls dynamically:

constructor(private fb: FormBuilder) {  }

// build form
this.userForm = this.fb.group({
  numbers: this.fb.array([
    new FormControl()
  ])
});


// push new form control when user clicks add button
addNumber() {
  const control = <FormArray>this.userForm.controls['numbers'];
  control.push(new FormControl())
}

And then your template:

<form [formGroup]="userForm" (ngSubmit)="submit(userForm.value)">
<div formArrayName="numbers">
  <!-- iterate the array of phone numbers -->
  <div *ngFor="let number of userForm.controls.numbers.controls; let i = index" >
      <label>PhoneNumber {{i+1}} </label>
      <input formControlName="{{i}}" />
  </div>
</div>
<button type="submit">Submit</button>
</form>

Demo