javascript - 为什么@angular 表单中没有 FormArrayDirective？

Question

根据最新版本的 Angular ，@angular/forms 导出以下内容:

export {FormControlDirective} from './directives/reactive_directives/form_control_directive';
export {FormControlName} from './directives/reactive_directives/form_control_name';
export {FormGroupDirective} from './directives/reactive_directives/form_group_directive';
export {FormArrayName} from './directives/reactive_directives/form_group_name';
export {FormGroupName} from './directives/reactive_directives/form_group_name';

FormContolName和 FormControlDirective , FormGroupName和 FormGroupDirective , 但是 FormArrayName没有 FormArrayDirective ， 为什么？

Answer 1

我认为这是不必要的。好吧，你可以创建指令，有些像

@Directive({
  selector: '[formArrayName]'
})
export class FormArrayDirective implements OnInit {
  formArray: FormArray;
  constructor(
    private el: ElementRef,
    @Host() @Optional() public form: FormGroupDirective
  ) {}
  ngOnInit() {
    this.formArray = this.form
      ? (this.form.form.get(
          this.el.nativeElement.getAttribute('formArrayName')
        ) as FormArray)
      : null;
  }
}

更新 在我们有 FormGroupDirective 之前，我认为最好有 FormGroup
新指令

@Directive({
  selector: '[formArrayName]'
})
export class FormArrayDirective implements OnInit {
  formArray: FormArray;
  form:FormGroup;
  constructor(
    private el: ElementRef,
    @Host() @Optional() private formDirective: FormGroupDirective
  ) {}
  ngOnInit() {
    this.formArray = this.formDirective
      ? (this.formDirective.form.get(
          this.el.nativeElement.getAttribute('formArrayName')
        ) as FormArray)
      : null;
      this.form=this.formDirective?this.formDirective.form:null
  }
}

该指令公开了两个属性: form和 formArray ，但请注意，您只能从具有 @ViewChild(FormArrayDirective) 的组件访问此属性。在 ngAfterViewInit 中
好奇心，得到它的目的是什么？