从反应式表单Angular 4的下拉列表中选择另一个值后清除FormArray

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup, FormArray } from '@angular/forms';

@Component({
  selector: 'app-your-component',
  templateUrl: './your-component.component.html',
  styleUrls: ['./your-component.component.css']
})
export class YourComponent implements OnInit {
  form: FormGroup;

  constructor(private formBuilder: FormBuilder) { }

  ngOnInit() {
    this.form = this.formBuilder.group({
      dropdown: '',
      formArray: this.formBuilder.array([])
    });
  }
}

<form [formGroup]="form">
  <select formControlName="dropdown" (change)="clearFormArray()">
    <option value="">Select an option</option>
    <option value="option1">Option 1</option>
    <option value="option2">Option 2</option>
  </select>

  <div formArrayName="formArray">
    <div *ngFor="let control of formArray.controls; let i = index">
      <input [formControlName]="i" placeholder="Value {{ i + 1 }}">
    </div>
  </div>
</form>

clearFormArray() {
  const formArray = this.form.get('formArray') as FormArray;
  formArray.clear();
}