如何有条件地展示用于Angular应用的Rxweb反应模式验证器？

npm install @rxweb/reactive-form-validators

import { required, email } from '@rxweb/reactive-form-validators';

<input type="text" formControlName="email" [class.is-invalid]="email.invalid && email.touched">
<div *ngIf="email.invalid && email.touched" class="invalid-feedback">
  <div *ngIf="email.errors.required">邮箱地址是必填的。</div>
  <div *ngIf="email.errors.email">请输入有效的邮箱地址。</div>
</div>

import { Component } from '@angular/core';
import { FormGroup, FormBuilder } from '@angular/forms';
import { required, email } from '@rxweb/reactive-form-validators';

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

  constructor(private fb: FormBuilder) {
    this.form = this.fb.group({
      email: ['', [required(), email()]]
    });
  }
}