如何手动将Angular表单字段设置为无效？

我正在使用登录表单，如果用户输入无效的凭据，我们希望将电子邮件和密码字段都标记为无效，并显示一条消息，指出登录失败。如何从可观察的回调中将这些字段设置为无效？

模板：

<form #loginForm="ngForm" (ngSubmit)="login(loginForm)" id="loginForm">
  <div class="login-content" fxLayout="column" fxLayoutAlign="start stretch">
    <md-input-container>
      <input mdInput placeholder="Email" type="email" name="email" required [(ngModel)]="email">
    </md-input-container>
    <md-input-container>
      <input mdInput placeholder="Password" type="password" name="password" required [(ngModel)]="password">
    </md-input-container>
    <p class='error' *ngIf='loginFailed'>The email address or password is invalid.</p>
    <div class="extra-options" fxLayout="row" fxLayoutAlign="space-between center">
     <md-checkbox class="remember-me">Remember Me</md-checkbox>
      <a class="forgot-password" routerLink='/forgot-password'>Forgot Password?</a>
    </div>
    <button class="login-button" md-raised-button [disabled]="!loginForm.valid">SIGN IN</button>
     <p class="note">Don't have an account?<br/> <a [routerLink]="['/register']">Click here to create one</a></p>
   </div>
 </form>

登录方式：

 @ViewChild('loginForm') loginForm: HTMLFormElement;

 private login(formData: any): void {
    this.authService.login(formData).subscribe(res => {
      alert(`Congrats, you have logged in. We don't have anywhere to send you right now though, but congrats regardless!`);
    }, error => {
      this.loginFailed = true; // This displays the error message, I don't really like this, but that's another issue.
      this.loginForm.controls.email.invalid = true;
      this.loginForm.controls.password.invalid = true; 
    });
  }

除了将输入无效标志设置为true之外，我还尝试将email.valid标志设置为false，并将其也设置loginForm.invalid为true。这些都不会导致输入显示其无效状态。

在组件中：

formData.form.controls['email'].setErrors({'incorrect': true});

并在HTML中：

<input mdInput placeholder="Email" type="email" name="email" required [(ngModel)]="email"  #email="ngModel">
<div *ngIf="!email.valid">{{email.errors| json}}</div>

添加到朱莉娅·帕森科娃的答案

要在组件中设置验证错误：

formData.form.controls['email'].setErrors({'incorrect': true});

取消设置组件中的验证错误：

formData.form.controls['email'].setErrors(null);

小心使用来设置错误，null因为这将覆盖所有错误。如果要保留一些错误，则可能必须先检查是否存在其他错误：

if (isIncorrectOnlyError){
   formData.form.controls['email'].setErrors(null);
}

我试图以setErrors()模板形式在ngModelChange处理程序中调用。直到我等了一下，它才起作用setTimeout()：

模板：

<input type="password" [(ngModel)]="user.password" class="form-control" 
 id="password" name="password" required (ngModelChange)="checkPasswords()">

<input type="password" [(ngModel)]="pwConfirm" class="form-control"
 id="pwConfirm" name="pwConfirm" required (ngModelChange)="checkPasswords()"
 #pwConfirmModel="ngModel">

<div [hidden]="pwConfirmModel.valid || pwConfirmModel.pristine" class="alert-danger">
   Passwords do not match
</div>

零件：

@ViewChild('pwConfirmModel') pwConfirmModel: NgModel;

checkPasswords() {
  if (this.pwConfirm.length >= this.user.password.length &&
      this.pwConfirm !== this.user.password) {
    console.log('passwords do not match');
    // setErrors() must be called after change detection runs
    setTimeout(() => this.pwConfirmModel.control.setErrors({'nomatch': true}) );
  } else {
    // to clear the error, we don't have to wait
    this.pwConfirmModel.control.setErrors(null);
  }
}

这样的陷阱使我更喜欢反应形式。

在材料2的新版本中，其控件名称以毡垫前缀setErrors（）开头不起作用，而是可以将Juila的答案更改为：

formData.form.controls['email'].markAsTouched();

这是一个有效的示例：

MatchPassword(AC: FormControl) {
  let dataForm = AC.parent;
  if(!dataForm) return null;

  var newPasswordRepeat = dataForm.get('newPasswordRepeat');
  let password = dataForm.get('newPassword').value;
  let confirmPassword = newPasswordRepeat.value;

  if(password != confirmPassword) {
    /* for newPasswordRepeat from current field "newPassword" */
    dataForm.controls["newPasswordRepeat"].setErrors( {MatchPassword: true} );
    if( newPasswordRepeat == AC ) {
      /* for current field "newPasswordRepeat" */
      return {newPasswordRepeat: {MatchPassword: true} };
    }
  } else {
    dataForm.controls["newPasswordRepeat"].setErrors( null );
  }
  return null;
}

createForm() {
  this.dataForm = this.fb.group({
    password: [ "", Validators.required ],
    newPassword: [ "", [ Validators.required, Validators.minLength(6), this.MatchPassword] ],
    newPasswordRepeat: [ "", [Validators.required, this.MatchPassword] ]
  });
}

在我的反应形式中，如果选中了另一个字段，则需要将一个字段标记为无效。在ng版本7中，我执行了以下操作：

    const checkboxField = this.form.get('<name of field>');
    const dropDownField = this.form.get('<name of field>');

    this.checkboxField$ = checkboxField.valueChanges
        .subscribe((checked: boolean) => {
            if(checked) {
                dropDownField.setValidators(Validators.required);
                dropDownField.setErrors({ required: true });
                dropDownField.markAsDirty();
            } else {
                dropDownField.clearValidators();
                dropDownField.markAsPristine();
            }
        });

因此，在上方，当我选中该复选框时，它会根据需要设置下拉菜单并将其标记为脏菜单。如果您未将其标记为此类，则在您尝试提交表单或与其交互之前，它不会无效（错误）。

如果复选框设置为false（未选中），则我们清除下拉列表中所需的验证器，并将其重置为原始状态。

另外-记得退订监视字段更改！

您也可以将viewChild'type'更改为NgForm，如下所示：

@ViewChild('loginForm') loginForm: NgForm;

然后以@Julia提到的相同方式引用您的控件：

 private login(formData: any): void {
    this.authService.login(formData).subscribe(res => {
      alert(`Congrats, you have logged in. We don't have anywhere to send you right now though, but congrats regardless!`);
    }, error => {
      this.loginFailed = true; // This displays the error message, I don't really like this, but that's another issue.

      this.loginForm.controls['email'].setErrors({ 'incorrect': true});
      this.loginForm.controls['password'].setErrors({ 'incorrect': true});
    });
  }

将错误设置为null将清除UI上的错误：

this.loginForm.controls['email'].setErrors(null);

虽然它晚了但是下面的解决方案对我有用。

    let control = this.registerForm.controls['controlName'];
    control.setErrors({backend: {someProp: "Invalid Data"}});
    let message = control.errors['backend'].someProp;

对于单元测试：

spyOn(component.form, 'valid').and.returnValue(true);