如何在 Angular 8 中显示 FormGroup 错误

Question

I have a textarea, which is required and needs at least 10 characters. If the user clicks the button and these criteria are true , I'd like to display an error message.

Here is my HTML-Code:

<form [formGroup]="formGrp" (submit)="onSubmit()">
  <div class="input-field input-field--multiline">
    <textarea 
      rows="2"
      [formControl]="requestAccessMessageCtrl"
      [attr.placeholder]="Your message">
    </textarea>
    <!--add error message here-->
  </div>
  <div class="button-group button-group--responsive request__btn">
    <button class="button button--primary" type="submit">Send</button>
  </div>
</form>

And here is my TypeScript:

readonly requestAccessMessageCtrl = new FormControl(null, {
    validators: [Validators.required, Validators.minLength(10)],
  })
readonly formGrp = new FormGroup({ message: this.requestAccessMessageCtrl })

onSubmit() {
  if (this.requestAccessMessageCtrl.invalid) {
    return;
  }
  this.userService.postActivity(
    this.requestAccessMessageCtrl.value,
  )
}

What do I have to add to display two error messages:

1. "Input field is required"
2. "Type at least 10 characters"

I'd like to display the errors only if the user has pressed the submit button.

Answer 1

Try this:

public isSubmitted;

and inside your submit() function set that variable to true. and then in your html add it to your conditions.

<div class="text-danger" *ngIf="isSubmitted && requestAccessMessageCtrl.invalid && requestAccessMessageCtrl.errors?.minlength ">
      <small>Need at least 10 characters</small>
</div>

<div class="text-danger" *ngIf="isSubmitted && requestAccessMessageCtrl.invalid && requestAccessMessageCtrl.errors?.required">
           <small>Field is required</small>
</div>

Answer 2

Add below in css file

.invalid {
    border-color: red;
    }

Add below code in ts file

<div class="input-field input-field--multiline">
        <textarea rows="2"
            [ngClass]="{'invalid':isSubmitted && requestAccessMessageCtrl.invalid && requestAccessMessageCtrl.errors?.minlength}"
            [formControl]="requestAccessMessageCtrl" [attr.placeholder]="Your message">
                    </textarea>
<div class="text-danger"
            *ngIf="isSubmitted && requestAccessMessageCtrl.invalid && requestAccessMessageCtrl.errors?.minlength ">
            <small>Need at least 10 characters</small>
</div>
<div class="text-danger"
            *ngIf="isSubmitted && requestAccessMessageCtrl.invalid && requestAccessMessageCtrl.errors?.required">
            <small>Field is required</small>
 </div></div>
<div class="button-group button-group--responsive request__btn">
    <button class="button button--primary" type="submit">Send</button>
</div>

Answer 3

please find the code below-

html-

    <form [formGroup]="formGrp">
    <div class="input-field input-field--multiline">
        <textarea
      rows="2"
      formControlName="message"
      >
    </textarea>
        <div *ngIf="showError">
            <span *ngIf="formGrp.get('message').errors?.required">Input field is required</span>
            <span *ngIf="formGrp.get('message').errors?.minlength">Type at least 10 characters</span>
        </div>
        <!--add error message here-->
    </div>
    <div class="button-group button-group--responsive request__btn">
        <button class="button button--primary" (click)="onSubmit()"type="submit">Send</button>
    </div>
</form>

and in the component-

showError = false;
    onSubmit() {
    if (this.requestAccessMessageCtrl.invalid) {
      this.showError = true;
      return;
  }
    this.showError = false;
}

Here is a stackblitz demo