我想使用反应形式和角度材料一次显示一个错误

Question

我正在使用 Angular 反应形式和 Angular 材料。我的代码运行良好。但我想一次显示一个错误

我的 .html 文件代码

      <form [formGroup]="accountDetailsForm" novalidate (ngSubmit)="onSubmitAccountDetails(accountDetailsForm.value)">

        <mat-form-field class="full-width">
          <input matInput maxlength="25" placeholder="Username" formControlName="username" required>
          <mat-error *ngFor="let validation of account_validation_messages.username">
            <mat-error class="error-message" *ngIf="accountDetailsForm.get('username').hasError(validation.type) && (accountDetailsForm.get('username').dirty || accountDetailsForm.get('username').touched)">{{validation.message}}</mat-error>
          </mat-error>
        </mat-form-field>

        <mat-form-field class="full-width">
          <input matInput type="email" placeholder="Email" formControlName="email" required>
          <mat-error *ngFor="let validation of account_validation_messages.email">
            <mat-error class="error-message" *ngIf="accountDetailsForm.get('email').hasError(validation.type) && (accountDetailsForm.get('email').dirty || accountDetailsForm.get('email').touched)">{{validation.message}}</mat-error>
          </mat-error>
        </mat-form-field>


        <div formGroupName="matching_passwords">
          <mat-form-field class="full-width">
            <input matInput type="password" placeholder="Password" formControlName="password" required>
            <mat-error *ngFor="let validation of account_validation_messages.password">
              <mat-error class="error-message" *ngIf="accountDetailsForm.get('matching_passwords').get('password').hasError(validation.type) && (accountDetailsForm.get('matching_passwords').get('password').dirty || accountDetailsForm.get('matching_passwords').get('password').touched)">{{validation.message}}</mat-error>
            </mat-error>
          </mat-form-field>

          <mat-form-field class="full-width">
            <input matInput type="password" placeholder="Confirm Password" formControlName="confirm_password"  [errorStateMatcher]="parentErrorStateMatcher" required>
            <mat-error *ngFor="let validation of account_validation_messages.confirm_password">
              <mat-error class="error-message" *ngIf="(accountDetailsForm.get('matching_passwords').get('confirm_password').hasError(validation.type)|| accountDetailsForm.get('matching_passwords').hasError(validation.type)) && (accountDetailsForm.get('matching_passwords').get('confirm_password').dirty || accountDetailsForm.get('matching_passwords').get('confirm_password').touched)">{{validation.message}}</mat-error>
            </mat-error>
          </mat-form-field>

        </div>

        <mat-checkbox formControlName="terms">
          I accept terms and conditions
        </mat-checkbox>
        <mat-error *ngFor="let validation of account_validation_messages.terms">
          <mat-error class="error-message" *ngIf="accountDetailsForm.get('terms').hasError(validation.type) && (accountDetailsForm.get('terms').dirty || accountDetailsForm.get('terms').touched)">{{validation.message}}</mat-error>
        </mat-error>

        <button class="submit-btn" color="primary" mat-raised-button type="submit" [disabled]="!accountDetailsForm.valid">
          Submit
        </button>

      </form>

    

我的 .ts 文件代码

在这里，我指定了错误的错误消息

account_validation_messages = {
    'username': [
      { type: 'required', message: 'Username is required' },
      { type: 'minlength', message: 'Username must be at least 5 characters long' },
      { type: 'maxlength', message: 'Username cannot be more than 25 characters long' },
      { type: 'pattern', message: 'Your username must contain only numbers and letters' },
      { type: 'validUsername', message: 'Your username has already been taken' }
    ],
    'email': [
      { type: 'required', message: 'Email is required' },
      { type: 'pattern', message: 'Enter a valid email' }
    ],
    'confirm_password': [
      { type: 'required', message: 'Confirm password is required' },
      { type: 'areEqual', message: 'Password mismatch' }
    ],
    'password': [
      { type: 'required', message: 'Password is required' },
      { type: 'minlength', message: 'Password must be at least 5 characters long' },
      { type: 'pattern', message: 'Your password must contain at least one uppercase, one lowercase, and one number' }
    ],
    'terms': [
      { type: 'pattern', message: 'You must accept terms and conditions' }
    ]
  }
  
 

表单验证器

 this.accountDetailsForm = this.fb.group({
      username: new FormControl('', Validators.compose([
       UsernameValidator.validUsername,
       Validators.maxLength(25),
       Validators.minLength(5),
       Validators.pattern('^(?=.*[a-zA-Z])(?=.*[0-9])[a-zA-Z0-9]+$'),
       Validators.required
      ])),
      email: new FormControl('', Validators.compose([
        Validators.required,
        Validators.pattern('^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+.[a-zA-Z0-9-.]+$')
      ])),
      matching_passwords: this.matching_passwords_group,
      terms: new FormControl(false, Validators.pattern('true'))
    })

一切工作正常，但问题是我正在使用 ngFor 显示错误，但我想在 mat-error 的帮助下一次显示一个错误。

Answer 1

使用CSS

首先隐藏所有错误

mat-error {
  display: none;
}

然后仅显示每个表单字段的第一个错误：

mat-form-field mat-error:first-child {
  display: block;
}

或者只有表单的第一个错误

form mat-error:first-child {
  display: block;
}