Angular 6: Set empty form array field

Question

I'm using Angular 6. and Reactive form builder to build a form.

ngOnInit() {
    this.landingPageForm = this.formBuilder.group({
      title: new FormControl('', [
        Validators.required
      ]),
      description: new FormControl('', [
        Validators.required
      ]),
      faqs: this.formBuilder.array([
        this.createFaqFields()
      ]),
    });

    this._setFormValue();
}

createFaqFields(): FormGroup {
  return this.formBuilder.group({
    question: new FormControl(),
    answer: new FormControl()
  });
}

private _setFormValue() {
    if (this.product) {
      this.landingPageForm.setValue({
        title: this.product.info.title,
        description: '',
        faqs: [],
      });
    }
  }

I have to prefill few fields initially and faqs is an array field in which new fields are generated dynamically by calling

onClickAddFaqField(): void {
  this.faqFields = this.landingPageForm.get('faqs') as FormArray;
  this.faqFields.push(this.createFaqFields());
}

Initially, there is only one faq input field in HTML and that empty. But it is giving an error

"Must supply a value for form control at index: 0.

How can I initialize the array input field empty?

Answer 1

After trying all the answers and examples from different sources. This is how I solved it.

private _setFormValue() {
  if (this.product) {
    this.landingPageForm.setValue({
      title: this.product.info.title,
      description: '',
      faqs: [{
        question: '',
        answer: ''
      }],
    });
  }
}

Added question, answer with empty value as the first object to the faqs field.