Create a collection of values and assign it to a form control in Ionic 2

How can I set default values for ion-select with multiple choices using a reactive form in Angular?

FormA:FormGroup;

this.FormA = this.formBuilder.group({
      toppings:['',validators.required]
    });

<form [formGroup]="FormA">
  <ion-item>
     <ion-label>Toppings</ion-label>
     <ion-select multiple="true" formControlName="toppings">
       <ion-option>Bacon</ion-option>
       <ion-option>Black Olives</ion-option>
       <ion-option>Extra Cheese</ion-option>
       <ion-option>Mushrooms</ion-option>
     </ion-select>
  </ion-item>
</form>

I want Bacon and Mushrooms to be pre-selected by default. Any suggestions on how to achieve this in the toppings formControl initialization?

Answer №1

To start the process of setting up the formControl, begin by including a value attribute for each option so you can easily distinguish them:

<form [formGroup]="FormA">
  <ion-item>
     <ion-label>Toppings</ion-label>
     <ion-select multiple="true" formControlName="toppings">
       <ion-option value="bacon">Bacon</ion-option>
       <ion-option value="black-olives">Black Olives</ion-option>
       <ion-option value="extra-cheese">Extra Cheese</ion-option>
       <ion-option value="mushrooms">Mushrooms</ion-option>
     </ion-select>
  </ion-item>
</form>

After that, set up the control with an Array of strings matching the values of the value attribute:

FormA:FormGroup;

this.FormA = this.formBuilder.group({
  toppings:[['bacon', 'black-olives'],validators.required]
});

Answer №2

If you're looking to create a list of Radio buttons easily, one method is using ngFor to iterate through an array list. Here's how I approached it:

Within the HTML template:

<ion-row radio-group formControlName="toppings">

  <ion-col *ngFor="let topping of toppings" col-auto>
    <ion-item>
      <ion-radio item-left value="{{topping}}"></ion-radio>
      <ion-label>{{topping}}</ion-label>
    </ion-item>
  </ion-col>
</ion-row>

In the component file:

toppings: ['bacon', 'black-olives'];
FormA:FormGroup; 

this.FormA = this.formBuilder.group(
{ toppings:[''],Validators.required]});

I added an ion-row with the radio-group attribute in the HTML template and utilized formControlName tied to the Form Control. The ngFor loop allows for creating a column for each item in the toppings array with a RadioButton for each entry.

Ensure that the value property corresponds to your array values for functionality. This approach simplifies manual creation of Radio buttons.

To enhance code maintenance, I suggest storing arrays as constants in a separate file for application-wide use. By importing these arrays and assigning them to properties, any updates to the arrays will propagate throughout the application without changing multiple templates.

Example shared .ts file:

export const Toppings = ['bacon', 'cheese' , 'olives'];
export const Base = ['Thick', 'Thin' , 'Gluten Free'];

In your component file:

import { Toppings , Base } from 'location/of/your/file

//Use "=" when assigning constant arrays
toppings = Toppings;
base = Base;

Hopefully, this solution proves helpful for your development needs.

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