Angular2 -如何将表单上的`touched`属性设置为true

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

import { Component } from '@angular/core';
import { FormControl } from '@angular/forms';

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

  constructor() {
    this.myInputControl = new FormControl();
  }

  markInputAsTouched() {
    this.myInputControl.markAsTouched();
  }
}

<form #myForm="ngForm">
  <input type="text" name="myInput" [(ngModel)]="myValue">
  <button (click)="markInputAsTouched()">Submit</button>
</form>