在FormArray上为required和minlength设置formvalidator

import { Component } from '@angular/core';
import { FormGroup, FormArray, FormControl, Validators } from '@angular/forms';

@Component({
  selector: 'app-my-form',
  templateUrl: './my-form.component.html',
  styleUrls: ['./my-form.component.css']
})
export class MyFormComponent {
  myForm: FormGroup;

  constructor() {
    this.myForm = new FormGroup({
      myArray: new FormArray([])
    });
  }
}

constructor() {
  this.myForm = new FormGroup({
    myArray: new FormArray([
      new FormControl('', [Validators.required, Validators.minLength(3)]),
      new FormControl('', [Validators.required, Validators.minLength(5)])
    ])
  });
}

<form [formGroup]="myForm">
  <div formArrayName="myArray">
    <div *ngFor="let control of myForm.get('myArray').controls; let i = index">
      <input [formControlName]="i" type="text" placeholder="Item {{ i + 1 }}">
      <div *ngIf="myForm.get('myArray').controls[i].invalid && myForm.get('myArray').controls[i].touched">
        <div *ngIf="myForm.get('myArray').controls[i].hasError('required')">This field is required.</div>
        <div *ngIf="myForm.get('myArray').controls[i].hasError('minlength')">Minimum length is 3 characters.</div>
      </div>
    </div>
  </div>
</form>