无法在Angular2`中获取错误消息

<form #myForm="ngForm">
  <input type="text" name="myInput" [(ngModel)]="myInputValue">
</form>

import { Component, ViewChild } from '@angular/core';

@Component({
  selector: 'my-component',
  template: `
    <form #myForm="ngForm">
      <input type="text" name="myInput" [(ngModel)]="myInputValue">
    </form>
  `
})
export class MyComponent {
  @ViewChild('myForm') myForm: NgForm;

  submitForm() {
    if (this.myForm.invalid) {
      // 获取错误消息
      const errors = this.myForm.controls['myInput'].errors;
      console.log(errors);
    }
  }
}