Question

我正在使用Angular 6。和Reactive form builder建立表单。

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: [],
      });
    }
  }

我必须在开始时预填充几个字段，faqs是一个数组字段，在其中通过调用

动态生成新字段

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

最初，HTML中只有一个常见问题输入字段，并且为空。但这是一个错误

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

如何将数组输入字段初始化为空？

Answer 1

我想我会这样做：

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

  // Try this
  // OTOH why when you set that to [] in _setFormValue()?
  this.landingPageForm.get('faqs').push(this.createFaqFields());

  this._setFormValue();
}

createFaqFields(): FormGroup {
  return new FormGroup({
    question: new FormControl(null),
    answer: new FormControl(null)
  });
}

Answer 2

代替在createFaqFields（）中使用FormControl（），尝试这样，

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


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

Answer 3

尝试了不同来源的所有答案和示例后。这就是我解决的方法。

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

在第question, answer字段中添加了faqs（空值）作为第一个对象。

角度6：设置空表格数组字段

3 个答案: