typescript - Angular Material - show mat-error on button click

Typescript - Angular Material - show mat-error on button click

To show a mat-error message in Angular Material upon clicking a button, you typically need to control the visibility of the error message programmatically. Here's how you can achieve this using Angular and TypeScript:

Example Setup

Assume you have an Angular component with a form and a button. The form has an input field with validation that shows a mat-error message based on certain conditions.

HTML Template (component.html)

<form #myForm="ngForm"> <mat-form-field> <input matInput placeholder="Username" name="username" required> <mat-error *ngIf="myForm.controls['username'].invalid && (myForm.controls['username'].dirty || myForm.controls['username'].touched)"> Username is required. </mat-error> </mat-form-field> <button mat-raised-button (click)="showError()">Show Error</button> </form>

TypeScript Component (component.ts)

In your component TypeScript file, define a method showError() that toggles a boolean flag to control the visibility of the error message.

import { Component } from '@angular/core'; @Component({ selector: 'app-my-component', templateUrl: './my-component.component.html', styleUrls: ['./my-component.component.css'] }) export class MyComponent { constructor() { } showError() { // You can perform additional logic here if needed // For simplicity, toggling a boolean flag to show/hide error this.showErrorMessage = true; // Set this flag to true to show the error message } }

CSS (Optional) - (component.css)

/* Define styles for error message if needed */

Explanation

  1. HTML Template:

    • Uses Angular Material's mat-form-field and mat-error directives.
    • The mat-error directive displays an error message if the input field is invalid and has been touched or is dirty (changed).
    • Includes a button (mat-raised-button) that triggers the showError() method on click.

  2. TypeScript Component:

    • Defines a boolean property showErrorMessage which controls the visibility of the error message.
    • The showError() method sets showErrorMessage to true, which triggers the display of the error message based on the condition defined in the HTML template.

  3. CSS (Optional):

    • You can define custom styles in the CSS file for the error message or form field if needed.

Notes

  • Form Validation: Ensure your form validation logic (required, minLength, etc.) is set up correctly in the template (*ngIf condition in mat-error).
  • Error Message Control: You can extend the showError() method to perform additional logic such as form validation checks or custom error handling.
  • Styling: Customize the appearance of the error message using CSS as per your application's design requirements.

By following these steps, you can show and control the visibility of mat-error messages in Angular Material upon clicking a button in your Angular component. Adjust the code according to your specific form validation rules and application needs.

Examples

  1. Show mat-error on button click in Angular Material form validation. Description: Implementing a button click event to trigger the display of mat-error in an Angular Material form.

    import { Component } from '@angular/core'; import { FormControl, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { emailFormControl = new FormControl('', [ Validators.required, Validators.email, ]); // Method to trigger validation and show errors showError() { this.emailFormControl.markAsTouched(); } } 
    <!-- form-validation.component.html --> <mat-form-field> <input matInput placeholder="Email" [formControl]="emailFormControl"> <mat-error *ngIf="emailFormControl.hasError('required')"> Email is required </mat-error> <mat-error *ngIf="emailFormControl.hasError('email')"> Please enter a valid email address </mat-error> </mat-form-field> <button mat-button (click)="showError()">Show Error</button>

  2. Angular Material mat-error display on button click using ngIf. Description: Utilizing ngIf directive to conditionally display mat-error upon button click in Angular Material.

    import { Component } from '@angular/core'; import { FormControl, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { emailFormControl = new FormControl('', [ Validators.required, Validators.email, ]); showError = false; // Method to toggle error display toggleError() { this.showError = !this.showError; } } 
    <!-- form-validation.component.html --> <mat-form-field> <input matInput placeholder="Email" [formControl]="emailFormControl"> <mat-error *ngIf="showError && emailFormControl.hasError('required')"> Email is required </mat-error> <mat-error *ngIf="showError && emailFormControl.hasError('email')"> Please enter a valid email address </mat-error> </mat-form-field> <button mat-button (click)="toggleError()">Toggle Error</button>

  3. Angular Material mat-error visibility on button click with FormGroup. Description: Handling mat-error visibility using FormGroup and button click event in Angular Material.

    import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { formGroup: FormGroup; constructor(private formBuilder: FormBuilder) { this.formGroup = this.formBuilder.group({ email: ['', [Validators.required, Validators.email]] }); } // Method to trigger validation and show errors showError() { Object.values(this.formGroup.controls).forEach(control => { control.markAsTouched(); }); } } 
    <!-- form-validation.component.html --> <form [formGroup]="formGroup"> <mat-form-field> <input matInput placeholder="Email" formControlName="email"> <mat-error *ngIf="formGroup.get('email').invalid && (formGroup.get('email').dirty || formGroup.get('email').touched)"> <span *ngIf="formGroup.get('email').errors.required"> Email is required </span> <span *ngIf="formGroup.get('email').errors.email"> Please enter a valid email address </span> </mat-error> </mat-form-field> <button mat-button type="button" (click)="showError()">Show Error</button> </form>

  4. Angular Material mat-error display on button click with Reactive Forms. Description: Demonstrating mat-error display triggered by button click using Reactive Forms in Angular Material.

    import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { formGroup: FormGroup; constructor(private formBuilder: FormBuilder) { this.formGroup = this.formBuilder.group({ email: ['', [Validators.required, Validators.email]] }); } // Method to trigger validation and show errors showError() { this.formGroup.get('email').markAsTouched(); } } 
    <!-- form-validation.component.html --> <form [formGroup]="formGroup"> <mat-form-field> <input matInput placeholder="Email" formControlName="email"> <mat-error *ngIf="formGroup.get('email').invalid && (formGroup.get('email').dirty || formGroup.get('email').touched)"> <span *ngIf="formGroup.get('email').errors.required"> Email is required </span> <span *ngIf="formGroup.get('email').errors.email"> Please enter a valid email address </span> </mat-error> </mat-form-field> <button mat-button type="button" (click)="showError()">Show Error</button> </form>

  5. Angular Material form validation with mat-error visibility toggle on button click. Description: Implementing a toggle mechanism to show/hide mat-error on button click in Angular Material form validation.

    import { Component } from '@angular/core'; import { FormControl, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { emailFormControl = new FormControl('', [ Validators.required, Validators.email, ]); showError = false; // Method to toggle error display toggleError() { this.showError = !this.showError; } } 
    <!-- form-validation.component.html --> <mat-form-field> <input matInput placeholder="Email" [formControl]="emailFormControl"> <mat-error *ngIf="showError && emailFormControl.hasError('required')"> Email is required </mat-error> <mat-error *ngIf="showError && emailFormControl.hasError('email')"> Please enter a valid email address </mat-error> </mat-form-field> <button mat-button (click)="toggleError()">Toggle Error</button>

  6. Angular Material mat-error visibility based on button click event using Template-driven Forms. Description: Controlling mat-error visibility based on button click event using Template-driven Forms in Angular Material.

    <!-- form-validation.component.html --> <form #form="ngForm"> <mat-form-field> <input matInput placeholder="Email" name="email" ngModel required email> <mat-error *ngIf="form.submitted && form.controls.email.invalid"> <span *ngIf="form.controls.email.errors.required"> Email is required </span> <span *ngIf="form.controls.email.errors.email"> Please enter a valid email address </span> </mat-error> </mat-form-field> <button mat-button type="button" (click)="form.submitted = true">Show Error</button> </form>

  7. Angular Material mat-error display controlled by button click event using FormGroup and Reactive Forms. Description: Handling mat-error display controlled by button click event using FormGroup and Reactive Forms in Angular Material.

    import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { formGroup: FormGroup; constructor(private formBuilder: FormBuilder) { this.formGroup = this.formBuilder.group({ email: ['', [Validators.required, Validators.email]] }); } // Method to trigger validation and show errors showError() { this.formGroup.get('email').markAsTouched(); } } 
    <!-- form-validation.component.html --> <form [formGroup]="formGroup"> <mat-form-field> <input matInput placeholder="Email" formControlName="email"> <mat-error *ngIf="formGroup.get('email').invalid && (formGroup.get('email').dirty || formGroup.get('email').touched)"> <span *ngIf="formGroup.get('email').errors.required"> Email is required </span> <span *ngIf="formGroup.get('email').errors.email"> Please enter a valid email address </span> </mat-error> </mat-form-field> <button mat-button type="button" (click)="showError()">Show Error</button> </form>

  8. Angular Material mat-error visibility toggle with custom error message on button click. Description: Implementing a button click event to toggle mat-error visibility with custom error messages in Angular Material.

    import { Component } from '@angular/core'; import { FormControl, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { emailFormControl = new FormControl('', [ Validators.required, Validators.email, ]); showError = false; // Method to toggle error display toggleError() { this.showError = !this.showError; } } 
    <!-- form-validation.component.html --> <mat-form-field> <input matInput placeholder="Email" [formControl]="emailFormControl"> <mat-error *ngIf="showError && emailFormControl.hasError('required')"> Custom required message </mat-error> <mat-error *ngIf="showError && emailFormControl.hasError('email')"> Custom email validation message </mat-error> </mat-form-field> <button mat-button (click)="toggleError()">Toggle Error</button>

  9. Angular Material mat-error visibility controlled by button click event with FormGroup and Validation. Description: Controlling mat-error visibility based on button click event using FormGroup and validation in Angular Material.

    import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { formGroup: FormGroup; constructor(private formBuilder: FormBuilder) { this.formGroup = this.formBuilder.group({ email: ['', [Validators.required, Validators.email]] }); } // Method to trigger validation and show errors showError() { this.formGroup.get('email').markAsTouched(); } } 
    <!-- form-validation.component.html --> <form [formGroup]="formGroup"> <mat-form-field> <input matInput placeholder="Email" formControlName="email"> <mat-error *ngIf="formGroup.get('email').invalid && (formGroup.get('email').dirty || formGroup.get('email').touched)"> <span *ngIf="formGroup.get('email').errors.required"> Email is required </span> <span *ngIf="formGroup.get('email').errors.email"> Please enter a valid email address </span> </mat-error> </mat-form-field> <button mat-button type="button" (click)="showError()">Show Error</button> </form>

  10. Angular Material mat-error display on button click with FormControl and Reactive Forms. Description: Demonstrating mat-error display based on button click event using FormControl and Reactive Forms in Angular Material.

    import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-form-validation', templateUrl: './form-validation.component.html', styleUrls: ['./form-validation.component.css'] }) export class FormValidationComponent { formGroup: FormGroup; constructor(private formBuilder: FormBuilder) { this.formGroup = this.formBuilder.group({ email: ['', [Validators.required, Validators.email]] }); } // Method to trigger validation and show errors showError() { this.formGroup.get('email').markAsTouched(); } } 
    <!-- form-validation.component.html --> <form [formGroup]="formGroup"> <mat-form-field> <input matInput placeholder="Email" formControlName="email"> <mat-error *ngIf="formGroup.get('email').invalid && (formGroup.get('email').dirty || formGroup.get('email').touched)"> <span *ngIf="formGroup.get('email').errors.required"> Email is required </span> <span *ngIf="formGroup.get('email').errors.email"> Please enter a valid email address </span> </mat-error> </mat-form-field> <button mat-button type="button" (click)="showError()">Show Error</button> </form>

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