如果未选中复选框，则设置复选框验证

Question

在我的 Angular 6 应用程序注册表中，我有一个已选中的复选框。我需要检查用户是否已取消选中该复选框，如果是，我想显示一条错误消息。

这是我在 .html 文件中的复选框，

 <div class="form-group">
       <div class="round">
            <input
                  type="checkbox"
                  id="checkbox33"
                  formControlName="agree">
             <label for="checkbox33"></label>
        </div>
        <small class="text-muted">Agree to our <a href="#" class="link">Terms
                  Of Use</a> and <a href="#" class="link">Privacy Policy</a>.
                </small>
        <span *ngIf="!worldWideRegisterForm.get('agree').valid" class="text-danger">You should agree!</span>

  </div>

这是我在 .ts 文件中的 ngOnInit()

ngOnInit() {
    this.worldWideRegisterForm = new FormGroup({
      'userName': new FormGroup({
        firstName: new FormControl(null, Validators.required),
        lastName: new FormControl(null, Validators.required)
      }),
      'email': new FormControl(null, [Validators.required, Validators.email]),
      'phone': new FormControl(null, Validators.required),
      'address': new FormGroup({
        line1: new FormControl(null, Validators.required),
        line2: new FormControl(null),
      }),
      'area': new FormGroup({
        'province': new FormControl(null, Validators.required),
        'city': new FormControl(null, Validators.required),
        'postalCode': new FormControl(null, Validators.required),
      }),
      'password': new FormControl(null, [Validators.required, Validators.minLength(6)]),
      'agree': new FormControl(true, Validators.required)
    });
  }

Answer 1

使用角度验证器 requiredTrue

'agree': new FormControl(true, Validators.requiredTrue)

对于错误

<div *ngIf="myTrue.hasError('required')">
   Agree the T&C    
</div>

官方链接https://angular.io/api/forms/Validators#requiredTrue