NativeScript + Bootstrap + Angular 2 - Simple Radio Button

RadioButton.ts

import { Component } from "@angular/core";

const defaultCssClass = " btn btn-secondary round-button ";
const activeCssClass = " btn btn-primary round-button active ";

@Component({
    template: `<StackLayout>
                  <WrapLayout orientation="horizontal">
                      <Label [text]="radioText" textWrap="true" style="font-size: 24px;"></Label>
                      <Button text="" (tap)="onClick()" [class]="btnClass" ></Button>          
                  </WrapLayout>
               </StackLayout>`,
    styles: [`.round-button { width: 30px; 
               height: 30px;
               margin-left: 5%; 
               border-radius: 15px; 
               border-width: 2px; 
               border-color: solid black; } `]
})
export class RadioButtonComponent {
    btnClass = defaultCssClass;
    radioText = " Radio Button random text";
    isSelected = false;

    constructor(){}

    onClick(){
        this.isSelected = !this.isSelected;
        this.btnClass = this.isSelected? defaultCssClass : activeCssClass ;
        
    }
}