Angular2 get existing validators of a formcontrol

Angular2 get existing validators of a formcontrol

In Angular, you can access the existing validators of a FormControl by using the validator property of the control. Here's how to do it:

Step 1: Setup Reactive Form

First, ensure you have a reactive form set up in your component.

example.component.ts:

import { Component, OnInit } from '@angular/core'; import { FormBuilder, FormGroup, Validators, AbstractControl } from '@angular/forms'; @Component({ selector: 'app-example', templateUrl: './example.component.html', }) export class ExampleComponent implements OnInit { myForm: FormGroup; constructor(private fb: FormBuilder) {} ngOnInit() { this.myForm = this.fb.group({ myControl: ['', [Validators.required, Validators.minLength(5)]], }); } getValidators(control: AbstractControl) { return control.validator ? control.validator(control) : null; } showValidators() { const control = this.myForm.get('myControl'); const errors = this.getValidators(control); console.log(errors); } }

Step 2: Create the Template

Create a button in your template to trigger the function that shows the existing validators.

example.component.html:

<form [formGroup]="myForm"> <input formControlName="myControl" placeholder="Enter at least 5 characters" /> <button (click)="showValidators()">Show Validators</button> </form>

Explanation

  1. Get Validators: The getValidators method checks if the control has a validator function and calls it to get the current validation state.
  2. Display Errors: The showValidators method retrieves the control's validators and logs the errors to the console.

Conclusion

By accessing the validator property of a FormControl, you can retrieve and utilize existing validators in your Angular forms. Adjust the method as needed to handle different validation scenarios!

Examples

  1. angular2 get formcontrol validators

    • Description: Retrieve existing validators attached to a FormControl in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-validator-example', templateUrl: './validator-example.component.html', styleUrls: ['./validator-example.component.css'] }) export class ValidatorExampleComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ email: ['', [Validators.required, Validators.email]], password: ['', Validators.required] }); } getValidators(controlName: string) { return this.myForm.get(controlName).validator; } } 
      <!-- validator-example.component.html --> <div> Validators for email: {{ getValidators('email') | json }} </div>
    • Explanation: This code snippet demonstrates how to access and display the validators attached to the 'email' FormControl in Angular 2+.

  2. angular2 get formcontrol validators list

    • Description: Obtain a list of validators applied to a specific FormControl in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-validator-list', templateUrl: './validator-list.component.html', styleUrls: ['./validator-list.component.css'] }) export class ValidatorListComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ username: ['', [Validators.required, Validators.minLength(4)]], password: ['', Validators.required] }); } getValidatorsList(controlName: string) { const control = this.myForm.get(controlName); return control ? Object.keys(control.validator).map(key => key + ': ' + control.validator[key]) : []; } } 
      <!-- validator-list.component.html --> <div> Validators for username: <ul> <li *ngFor="let validator of getValidatorsList('username')">{{ validator }}</li> </ul> </div>
    • Explanation: This example showcases how to retrieve and display a list of validators (along with their parameters) applied to the 'username' FormControl.

  3. angular2 check if formcontrol has validators

    • Description: Determine if a FormControl has validators assigned in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-validator-check', templateUrl: './validator-check.component.html', styleUrls: ['./validator-check.component.css'] }) export class ValidatorCheckComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ age: ['', Validators.required], city: [''] }); } hasValidators(controlName: string) { const control = this.myForm.get(controlName); return control && control.validator !== null; } } 
      <!-- validator-check.component.html --> <div> Age field has validators: {{ hasValidators('age') ? 'Yes' : 'No' }} </div>
    • Explanation: This snippet demonstrates how to check if the 'age' FormControl has validators assigned in an Angular 2+ reactive form.

  4. angular2 get custom validator formcontrol

    • Description: Access a custom validator function attached to a FormControl in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators, AbstractControl } from '@angular/forms'; function customValidator(control: AbstractControl): { [key: string]: boolean } | null { // custom validation logic if (control.value !== 'custom') { return { 'customValidation': true }; } return null; } @Component({ selector: 'app-custom-validator', templateUrl: './custom-validator.component.html', styleUrls: ['./custom-validator.component.css'] }) export class CustomValidatorComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ customField: ['', customValidator], otherField: ['', Validators.required] }); } getCustomValidator(controlName: string) { const control = this.myForm.get(controlName); return control ? control.errors && control.errors['customValidation'] : false; } } 
      <!-- custom-validator.component.html --> <div> CustomField has custom validator: {{ getCustomValidator('customField') ? 'Yes' : 'No' }} </div>
    • Explanation: This example shows how to retrieve and check the presence of a custom validator ('customValidator') assigned to the 'customField' FormControl.

  5. angular2 get built-in validator formcontrol

    • Description: Retrieve a built-in validator (e.g., Validators.required) applied to a FormControl in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-built-in-validator', templateUrl: './built-in-validator.component.html', styleUrls: ['./built-in-validator.component.css'] }) export class BuiltInValidatorComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ requiredField: ['', Validators.required], emailField: ['', Validators.email] }); } getRequiredValidator(controlName: string) { const control = this.myForm.get(controlName); return control ? control.errors && control.errors['required'] : false; } } 
      <!-- built-in-validator.component.html --> <div> RequiredField has required validator: {{ getRequiredValidator('requiredField') ? 'Yes' : 'No' }} </div>
    • Explanation: This snippet demonstrates how to check if the 'requiredField' FormControl has the built-in 'required' validator applied in Angular 2+.

  6. angular2 get formcontrol validation errors

    • Description: Access validation errors for a FormControl in Angular 2+ reactive forms.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-validation-errors', templateUrl: './validation-errors.component.html', styleUrls: ['./validation-errors.component.css'] }) export class ValidationErrorsComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ username: ['', Validators.required], password: ['', Validators.minLength(6)] }); } getValidationErrors(controlName: string) { const control = this.myForm.get(controlName); return control ? control.errors : null; } } 
      <!-- validation-errors.component.html --> <div> Validation errors for username: {{ getValidationErrors('username') | json }} </div>
    • Explanation: This code sample illustrates how to retrieve and display validation errors for the 'username' FormControl in Angular 2+.

  7. angular2 get multiple formcontrol validators

    • Description: Retrieve multiple validators applied to a FormControl in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-multiple-validators', templateUrl: './multiple-validators.component.html', styleUrls: ['./multiple-validators.component.css'] }) export class MultipleValidatorsComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ phone: ['', [Validators.required, Validators.pattern('^\\+(?:[0-9] ?){6,14}[0-9]$')]], address: ['', Validators.maxLength(100)] }); } getValidatorsList(controlName: string) { const control = this.myForm.get(controlName); return control ? Object.keys(control.validator).map(key => key + ': ' + control.validator[key]) : []; } } 
      <!-- multiple-validators.component.html --> <div> Validators for phone: {{ getValidatorsList('phone') | json }} </div>
    • Explanation: This snippet showcases how to access and display multiple validators applied to the 'phone' FormControl in Angular 2+.

  8. angular2 check if formcontrol has specific validator

    • Description: Check if a specific validator (e.g., Validators.minLength) is applied to a FormControl in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-specific-validator', templateUrl: './specific-validator.component.html', styleUrls: ['./specific-validator.component.css'] }) export class SpecificValidatorComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ code: ['', Validators.minLength(4)] }); } hasMinLengthValidator(controlName: string) { const control = this.myForm.get(controlName); return control ? control.errors && control.errors['minlength'] : false; } } 
      <!-- specific-validator.component.html --> <div> Code field has minlength validator: {{ hasMinLengthValidator('code') ? 'Yes' : 'No' }} </div>
    • Explanation: This example demonstrates how to check if the 'code' FormControl has the Validators.minLength validator applied in Angular 2+.

  9. angular2 remove formcontrol validator

    • Description: Remove a validator from a FormControl dynamically in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; @Component({ selector: 'app-remove-validator', templateUrl: './remove-validator.component.html', styleUrls: ['./remove-validator.component.css'] }) export class RemoveValidatorComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ country: ['', Validators.required], zipCode: ['', Validators.pattern('[0-9]{5}')] }); } removeValidator(controlName: string, validator: ValidatorFn) { const control = this.myForm.get(controlName); if (control) { const validators = control.validator; delete validators[validator.name]; control.setValidators(validators); control.updateValueAndValidity(); } } } 
      <!-- remove-validator.component.html --> <div> <button (click)="removeValidator('zipCode', Validators.pattern)">Remove pattern validator</button> </div>
    • Explanation: This code snippet allows dynamically removing the Validators.pattern validator from the 'zipCode' FormControl in Angular 2+.

  10. angular2 add custom validator to formcontrol

    • Description: Attach a custom validator function dynamically to a FormControl in Angular 2+.
    • Code:
      import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators, AbstractControl, ValidatorFn } from '@angular/forms'; function customValidator(control: AbstractControl): { [key: string]: boolean } | null { // custom validation logic if (control.value !== 'custom') { return { 'customValidation': true }; } return null; } @Component({ selector: 'app-add-custom-validator', templateUrl: './add-custom-validator.component.html', styleUrls: ['./add-custom-validator.component.css'] }) export class AddCustomValidatorComponent { myForm: FormGroup; constructor(private fb: FormBuilder) { this.myForm = this.fb.group({ customField: ['', Validators.required], otherField: ['', Validators.required] }); } addCustomValidator(controlName: string, validator: ValidatorFn) { const control = this.myForm.get(controlName); if (control) { const validators = control.validator ? control.validator : {}; validators[validator.name] = validator; control.setValidators(Validators.compose(Object.values(validators))); control.updateValueAndValidity(); } } } 
      <!-- add-custom-validator.component.html --> <div> <button (click)="addCustomValidator('customField', customValidator)">Add custom validator</button> </div>
    • Explanation: This example demonstrates how to dynamically add a custom validator function ('customValidator') to the 'customField' FormControl in Angular 2+.

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