如何在Angular2 Reactive Forms中深度复制FormArray条目

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

constructor(private fb: FormBuilder) {
  this.myForm = this.fb.group({
    items: this.fb.array([])
  });
}

copyItem(index: number) {
  const item = this.myForm.get('items').at(index);
  const copiedItem = this.fb.group(item.value);
  this.myForm.get('items').insert(index + 1, copiedItem);
}

<div formArrayName="items">
  <div *ngFor="let item of myForm.get('items').controls; let i = index">
    <div [formGroupName]="i">
      <!-- 表单控件 -->
    </div>
    <button (click)="copyItem(i)">复制</button>
  </div>
</div>