Ionic uses the life-cycle events provided by the Angular. These life-cycle events are :
ngOnInit : It is fired once during component initialization. It can be used to initialize local members and make calls into services, which need to be done only once.
ngOnDestroy : It is fired just before Angular destroys the view. It can be useful for clean-up like unsubscribing from observables.
ionViewWillEnter : It is fired when the component routing-to is about to animate into view.
ionViewDidEnter : It is fired when the component routing-to has finished animating.
ionViewWillLeave : It is fired when the component routing-from is about to animate.
ionViewDidLeave : It is fired when the component routing-to has finished animating.
