Angular 2中的条件验证

import { Component } from '@angular/core';
import { FormBuilder, Validators } from '@angular/forms';

@Component({
  selector: 'app-form',
  template: `
    <form [formGroup]="myForm">
      <input formControlName="name" placeholder="Name">
      <div *ngIf="myForm.get('name').hasError('required') && myForm.get('name').touched">
        Name is required.
      </div>
      <div *ngIf="myForm.get('name').hasError('minlength') && myForm.get('name').touched">
        Name should have at least 3 characters.
      </div>
      <input formControlName="age" placeholder="Age">
      <div *ngIf="myForm.get('age').hasError('required') && myForm.get('age').touched">
        Age is required.
      </div>
      <div *ngIf="myForm.get('age').hasError('pattern') && myForm.get('age').touched">
        Age should be a number.
      </div>
    </form>
  `
})
export class FormComponent {
  myForm = this.fb.group({
    name: ['', [Validators.required, Validators.minLength(3)]],
    age: ['', [Validators.required, Validators.pattern(/^\d+$/)]]
  });

  constructor(private fb: FormBuilder) {}
}