angular 2 access自定义验证器返回通知用户

import { AbstractControl, ValidationErrors } from '@angular/forms';

export function passwordValidator(control: AbstractControl): ValidationErrors | null {
  const password = control.value;
  const pattern = /^(?=.*[A-Z])(?=.*[a-z])(?=.*\d).{8,}$/;

  if (password && !pattern.test(password)) {
    return { invalidPassword: true };
  }

  return null;
}

import { Component } from '@angular/core';
import { FormControl, FormGroup, Validators } from '@angular/forms';
import { passwordValidator } from './password.validator';

@Component({
  selector: 'app-password-form',
  template: `
    <form [formGroup]="form">
      <input type="password" formControlName="password">
      <div *ngIf="form.get('password').invalid && form.get('password').touched">
        <div *ngIf="form.get('password').hasError('required')">Password is required</div>
        <div *ngIf="form.get('password').hasError('invalidPassword')">Invalid password</div>
      </div>
    </form>
  `,
})
export class PasswordFormComponent {
  form: FormGroup;

  constructor() {
    this.form = new FormGroup({
      password: new FormControl('', [Validators.required, passwordValidator]),
    });
  }
}