问ionic3:如何连接单选按钮的值以连接到页面

EN

import { Storage } from '@ionic/storage';

firstOption: String;

export class Settings {
  constructor(private storage: Storage) { }

  ionViewWillEnter() { 
    this.setUpSettings();
  }

  optionSelected(option,value) {
    this.storage.set(option,value);
  }

  setUpSettings() {
    this.storage.get('firstOption').then((res) => {
      this.firstOption = res;
    });
  }
}

<ion-content>

  <ion-list radio-group [(ngModel)]="firstOption">

    <ion-item>
      <ion-label>BBC</ion-label>
      <ion-radio (ionSelect)="optionSelected('firstOption','bbc')" value="bbc"></ion-radio>
    </ion-item>

    <ion-item>
      <ion-label>CNN</ion-label>
      <ion-radio (ionSelect)="optionSelected('firstOption','cnn')" value="cnn"></ion-radio>
    </ion-item>

  </ion-list>

</ion-content>