如何生成FormArray项目？

<form [formGroup]="form">
  <div formArrayName="items">
    <div *ngFor="let item of items.controls; let i = index">
      <input type="text" [formControlName]="i">
    </div>
  </div>
</form>

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

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

  constructor(private fb: FormBuilder) { }

  ngOnInit() {
    this.form = this.fb.group({
      items: this.fb.array([])
    });
  }

  get items() {
    return this.form.get('items') as FormArray;
  }
}

ngOnInit() {
  this.form = this.fb.group({
    items: this.fb.array([
      this.createItem('Item 1'),
      this.createItem('Item 2'),
      this.createItem('Item 3')
    ])
  });
}

createItem(value: string) {
  return this.fb.control(value);
}

addItem() {
  this.items.push(this.createItem(''));
}

removeItem(index: number) {
  this.items.removeAt(index);
}

<button (click)="addItem()">Add Item</button>
<div *ngFor="let item of items.controls; let i = index">
  <input type="text" [formControlName]="i">
  <button (click)="removeItem(i)">Remove Item</button>
</div>