Ionic 4|5 Checkbox List Required Validation using Reactive Forms

In this article, we will discuss How to validate multiple checkboxes in Ionic 4|5 application using Angular Reactive Forms.

Here we will have a list of the checkbox which can be selected or unselected using a single master checkbox and also individually.

We will add validation on checkbox list using Reactive form approach provided by Angular core API.

Let’s get started with the implementation.

Version Check

@ionic/cli 

   _             _
  (_) ___  _ __ (_) ___
  | |/ _ \| '_ \| |/ __|
  | | (_) | | | | | (__
  |_|\___/|_| |_|_|\___| CLI 6.4.1

Update to the latest version of Ionic CLI by running following NPM command:

$ npm install -g @ionic/cli</pre>
<h3></h3>
<h3>Create an Ionic Application</h3>
Using <code>@ionic/cli we will create a new Ionic application using Angular framework with a blank template:
$ ionic new ionic-checkbox-validation blank --type=angular</pre>
 
<h3>Configuration for Angular Forms</h3>
To use forms in Angular application, we need to import <code>FormsModule and ReactiveFormsModule in the page module file.

As we are going to implement in Home Page so open home.module.ts file import these modules as shown below:
// home.module.ts
import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { IonicModule } from '@ionic/angular';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { RouterModule } from '@angular/router';

import { HomePage } from './home.page';

@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    ReactiveFormsModule,
    IonicModule,
    RouterModule.forChild([
      {
        path: '',
        component: HomePage
      }
    ])
  ],
  declarations: [HomePage]
})
export class HomePageModule { }

Home Page Template
Adding Form
In the Home page template HTML, we will add a form with [formBuilder] directive property. The form submit event will be handled by (ngSubmit) method on the form.
<form [formGroup]="ionicFormGroup" (ngSubmit)="submitForm()">
...
</form>

</pre>
 

<strong>Checkbox list</strong>

In the form element, define checkbox elements in <code>ion-list UI component directive. It will iterate over CHECK_LIST data object using *ngFor directive as shown below:
<ion-header [translucent]="true">
  <ion-toolbar>
    <ion-title>
      Ionic Multi Checkbox Validation
    </ion-title>
  </ion-toolbar>
</ion-header>

<ion-content [fullscreen]="true">

  <form [formGroup]="ionicForm" (ngSubmit)="submitForm()">

    <ion-list>

      <ion-item *ngFor="let item of CHECK_LIST; let i=index">

        <ion-label>{{item.name}}</ion-label>
        <ion-checkbox slot="end" [value]="item.value" [checked]="item.checked"
          (ionChange)="onSelectionChange($event,i)">
        </ion-checkbox>

      </ion-item>

      <ion-item *ngIf="isFormSubmitted && ionicForm.controls['checkboxArrayList'].errors?.required">
        <label class="error-msg">
          Please select Hobby!
        </label>
      </ion-item>

      <ion-item class="center">
        <ion-button type="submit">Submit Form</ion-button>
      </ion-item>

    </ion-list>

    {{CHECK_LIST | json}}

  </form>


</ion-content></pre>
In the above template, we have also added a <code>label element to show an error message when no checkbox is selected. This message will only be shown after a user submits the form as we have added a variable isFormSubmitted on *ngIf condition.
Home Component Class
The list of checkboxes will be created dynamically by iterating over the CHECK_LIST object will look like this:
  CHECK_LIST = [
    { name: 'Photography', value: 'Photography', checked: true },
    { name: 'Blogging', value: 'Blogging' },
    { name: 'Cooking', value: 'Cooking' },
    { name: 'Singing', value: 'Singing' },
    { name: 'Dancing', value: 'Dancing' },
    { name: 'Pottery', value: 'Pottery' },
    { name: 'Knitting', value: 'Knitting' }
  ];</pre>
We can set the <code>checked property to true, if you want to set it checked by default.

To instantiate the form as Reactive we will define the ionicForm as FormGroup.
ionicForm: FormGroup;</pre>
In the constructor, we will define checkbox list control as FormArray as shown below:
<pre class="wp-block-prismatic-blocks"><code class="language-javascript">  constructor(private formBuilder: FormBuilder) {
    this.ionicForm = this.formBuilder.group({
      checkboxArrayList: this.formBuilder.array([], [Validators.required])
    });
  }</pre>
To update the <code>checkboxArrayList on page load, we will update it in the updateCheckControl() method which will also be called from checkbox change event in the onSelectionChange() method.
  updateCheckControl(cal, o) {
    if (o.checked) {
      cal.push(new FormControl(o.value));
    } else {
      cal.controls.forEach((item: FormControl, index) => {
        if (item.value == o.value) {
          cal.removeAt(index);
          return;
        }
      });
    }
  }

  onLoadCheckboxStatus() {
    const checkboxArrayList: FormArray = this.ionicForm.get('checkboxArrayList') as FormArray;
    this.CHECK_LIST.forEach(o => {
      this.updateCheckControl(checkboxArrayList, o);
    })
  }

  onSelectionChange(e, i) {
    const checkboxArrayList: FormArray = this.ionicForm.get('checkboxArrayList') as FormArray;
    this.CHECK_LIST[i].checked = e.target.checked;
    this.updateCheckControl(checkboxArrayList, e.target);

  }

After adding the above methods the final home.page.ts file will look like this:
// home.page.ts
import { Component } from '@angular/core';
import { FormBuilder, FormGroup, FormArray, FormControl, Validators } from '@angular/forms';

@Component({
  selector: 'app-home',
  templateUrl: 'home.page.html',
  styleUrls: ['home.page.scss'],
})
export class HomePage {

  ionicForm: FormGroup;

  isFormSubmitted = false;

  CHECK_LIST = [
    { name: 'Photography', value: 'Photography', checked: true },
    { name: 'Blogging', value: 'Blogging' },
    { name: 'Cooking', value: 'Cooking' },
    { name: 'Singing', value: 'Singing' },
    { name: 'Dancing', value: 'Dancing' },
    { name: 'Pottery', value: 'Pottery' },
    { name: 'Knitting', value: 'Knitting' }
  ];

  constructor(private formBuilder: FormBuilder) {
    this.ionicForm = this.formBuilder.group({
      checkboxArrayList: this.formBuilder.array([], [Validators.required])
    });

    this.onLoadCheckboxStatus();
  }

  updateCheckControl(cal, o) {
    if (o.checked) {
      cal.push(new FormControl(o.value));
    } else {
      cal.controls.forEach((item: FormControl, index) => {
        if (item.value == o.value) {
          cal.removeAt(index);
          return;
        }
      });
    }
  }

  onLoadCheckboxStatus() {
    const checkboxArrayList: FormArray = this.ionicForm.get('checkboxArrayList') as FormArray;
    this.CHECK_LIST.forEach(o => {
      this.updateCheckControl(checkboxArrayList, o);
    })
  }

  onSelectionChange(e, i) {
    const checkboxArrayList: FormArray = this.ionicForm.get('checkboxArrayList') as FormArray;
    this.CHECK_LIST[i].checked = e.target.checked;
    this.updateCheckControl(checkboxArrayList, e.target);

  }

  submitForm() {
    this.isFormSubmitted = true;
    if (!this.ionicForm.valid) {
      console.log('Please provide all the required values!')
      return false;
    } else {
      console.log('Form Submitted', this.ionicForm.value)
    }
  }
}


 
In this tutorial, we implemented Reactive form validation on the checkbox list in Ionic 5 application. We added user Angular form core services to add validation on form. When no value is checked an error message is shown to the user. Thanks for reading!
 
 
 







 
Category: Ionic Framework