Angular 2. How to use array of objects for controls in Reactive Forms

Question

I need to dynamic create textarea for forms. I have the following model:

this.fields = {
      isRequired: true,
      type: {
        options: [
          {
            label: 'Option 1',
            value: '1'
          },
          {
            label: 'Option 2',
            value: '2'
          }
        ]
      }
    };

And form:

this.userForm = this.fb.group({
      isRequired: [this.fields.isRequired, Validators.required],
      //... here a lot of other controls
      type: this.fb.group({
         options: this.fb.array(this.fields.type.options),
      })
});

Part of template:

<div formGroupName="type">
       <div formArrayName="options">
         <div *ngFor="let option of userForm.controls.type.controls.options.controls; let i=index">
            <textarea [formControlName]="i"></textarea>
         </div>
      </div>
</div>

So, as you can see I have an array of objects and I want to use label property to show it in a textarea. Now I see [object Object]. If I change options to a simple string array, like: ['Option 1', 'Option 2'], then all works fine. But I need to use objects. So, instead of:

<textarea [formControlName]="i"></textarea>

I have tried:

<textarea [formControlName]="option[i].label"></textarea>

But, it doesn't work.
How can I use an array of objects?

This is Plunkr

Answer 1

You need to add a FormGroup, which contains your label and value. This also means that the object created by the form, is of the same build as your fields object.

ngOnInit() {
  // build form
  this.userForm = this.fb.group({
    type: this.fb.group({
      options: this.fb.array([]) // create empty form array   
    })
  });

  // patch the values from your object
  this.patch();
}

After that we patch the value with the method called in your OnInit:

patch() {
  const control = <FormArray>this.userForm.get('type.options');
  this.fields.type.options.forEach(x => {
    control.push(this.patchValues(x.label, x.value))
  });
}

// assign the values
patchValues(label, value) {
  return this.fb.group({
    label: [label],
    value: [value]
  })    
}

Finally, here is a

Demo