Radio button in Angular Reactive formArray - Select one item in an array

Question

I'm having a formArray namely "address" and this will be a dynamic, once the user clicks the "Add Address" button immediately one address form will add. Each address form has one radio button - User needs to select any of the address has a PRIMARY address (i.e., User needs to select one item in an array).

I refereed the following question but it now full-fill my requirement Angular formArray radio buttons in the said question each item has a group of radio button (i.e., selection within an item)

Working code is available in StackBlitz : https://stackblitz.com/edit/angular-reactiveform-radiobutton-in-arrayform

Source Code: AppComponent.ts

import { Component } from '@angular/core';
import { FormBuilder, FormGroup, FormArray, Validators } from '@angular/forms';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  name = 'Angular';
  public userForm: FormGroup;

  constructor(private _fb: FormBuilder) {
    this.userForm = this._fb.group({
      firstName: [],
      lastName: [],
      address: this._fb.array([this.addAddressGroup()])
    });
  }

  private addAddressGroup(): FormGroup {
    return this._fb.group({
      street: [],
      city: [],
      state: [],
      isPrimary: []
    });
  }

  get addressArray(): FormArray {
    return <FormArray>this.userForm.get('address');
  }

  addAddress(): void {
    this.addressArray.push(this.addAddressGroup());
  }

  removeAddress(index: number): void {
    this.addressArray.removeAt(index);
  }
}

Source Code: AppComponent.html

<form class="example-form" [formGroup]="userForm">
  <div>
    <mat-card class="example-card">
      <mat-card-header>
        <mat-card-title>Users Creation</mat-card-title>
      </mat-card-header>
      <mat-card-content>
        <div class="primary-container">
          <mat-form-field>
            <input matInput placeholder="First Name" value="" formControlName="firstName">
          </mat-form-field>
          <mat-form-field>
            <input matInput placeholder="Last Name" value="" formControlName="lastName">
          </mat-form-field>
        </div>
        <div formArrayName="address">
          <div class="address-container" *ngFor="let group of addressArray.controls; let i = index;"
            [formGroupName]="i">
            <fieldset>
              <legend>
                <h3>Address: {{i + 1}}</h3>
              </legend>
              <mat-radio-button class="example-radio-button" value="true" checked="true" formControlName="isPrimary">
                Primary
              </mat-radio-button>
              <div>
                <mat-form-field>
                  <input matInput placeholder="Street" value="" formControlName="street">
                </mat-form-field>
                <mat-form-field>
                  <input matInput placeholder="City" value="" formControlName="city">
                </mat-form-field>
                <mat-form-field>
                  <input matInput placeholder="State" value="" formControlName="state">
                </mat-form-field>
              </div>
            </fieldset>
          </div>
        </div>
        <div class="form-row org-desc-parent-margin">
          <button mat-raised-button (click)="addAddress()">Add more address</button>
        </div>
      </mat-card-content>
    </mat-card>
  </div>
</form>
<mat-card class="pre-code">
  <mat-card-header>
    <mat-card-title>Users Information</mat-card-title>
  </mat-card-header>
  <mat-card-content>
    <pre>{{userForm.value | json}}</pre>
  </mat-card-content>
</mat-card>

Kindly assist me how to select an address as a PRIMARY out of N number of address. Only one of the address property "isPrimary" should be true other items and all should be false

Answer 1

In a new project, I achieved this just using material components, without involving events / loops... the key is just to use the name property of the mat-radio-group to make all the iterations of the radio group behave as one.

<mat-radio-group [formControl]="userForm.controls.primary" name="primary">

I have also used a different approach for the "isPrimary" check. Instead of having a boolean property in every address instance, I used a single property "primary address index" inside the user model, so when you click on a radio button, the value of the primary field is updated using the index of the current element ([value]="i")

<mat-radio-button [value]="i">Primary</mat-radio-button>

this is my entire form

<form [formGroup]="userForm" (ngSubmit)="onSubmit()">
    name
    <input formControlName="name" /><br>
    email
    <input formControlName="email" /><br>
    VAT
    <input formControlName="VAT" /><br>

    <button (click)="addNewAddress()">Add new address</button><br>

    <div formArrayName="addresses">
        <div *ngFor="let address of userForm.get('addresses').controls; let i=index">
            <h3>ADDRESS {{i+1}}: </h3>
            primary
            <mat-radio-group [formControl]="userForm.controls.primary" name="primary">
                <mat-radio-button [value]="i">Primary
                </mat-radio-button>
            </mat-radio-group>


            <div [formGroupName]="i">
                street
                <input formControlName="street" /><br>
                city
                <input formControlName="city" /><br>
                country
                <input formControlName="country" /><br>
                zip
                <input formControlName="zip" /><br>

                <button (click)="deleteAddress(i)">
                    Delete <address></address>
                </button>
            </div>
        </div>
    </div>
    <button type="submit" [disabled]="userForm.pristine || !userForm.valid">Save</button>
</form>

here the ts relevant parts:

initForm() {
   this.detailForm = this.fb.group({
        name: ['', Validators.required],
        VAT: ['', Validators.required],
        fiscalCode: ['', Validators.required],
        legalEntity: ['',],
        email: ['', Validators.email],
        primary: [0, Validators.required], //when creating a new customer, set first address as primary
        addresses: this.fb.array([]),
      });
}

addNewAddress(addr: Address): void {
    let control = <FormArray>this.detailForm.controls.addresses;
    control.push(
      this.fb.group({
        street: ['', Validators.required],
        city: ['', Validators.required],
        country: ['', Validators.required],
        zip: [''],
      })
    );
  }

hope this can help!