Platform.ready().then(() => { not triggered in iOS

constructor(platform: Platform, statusBar: StatusBar, splashScreen: SplashScreen) {
   alert(platform.is("android"));
   alert(platform.is("ios"));
    platform.ready().then(() => {
      alert("ready")
      // Okay, so the platform is ready and our plugins are available.
      // Here you can do any higher level native things you might need.
      statusBar.styleDefault();
      splashScreen.hide();
    });
  }

on android device, ready alert is poped up but not on iOS device.
both android and iOS have nicely showing true or false to platform.is() method.

am I the only one who have this problem? or did I use platform.ready method wrongly?