differentiate betwwen forward and backward navigation on a page Ionic2 - ionic2

Question

How can I differentiate that whether a page comes into view from forward or backward navigation. I want to run some code only if it is forward navigation.

Answer 1

CASE 1 :- Say you are navigating from 1 page to another - Forward. I.e. using navCtrl.push(Page,params).
Here, you can put your code in constructor(){}. Code in your constructor always gets executed when you push/navigate to a page - Forward. (Rather than push, you can also reset the stack to a rootpage. This is valid then also.)
CASE 2 :- Say you are navigating back from a page - Backward. I.e. manually going back by user in the app or using navCtrl.pop().
Here, I think, there is NOT any in-built way to recognise if you have navigated on a back page. Here you need to build your own logic.
For e.g, PageA -> PageB is your navigation. I have used localStorage variable to set to some value, (e.g localStorage.setItem('isPushed',true)) when navigating from PageA -> PageB.
Now, in PageA I have written this code using ionViewWillEnter():
ionViewWillEnter(){
if(JSON.parse(localStorage.getItem('isPushed')){
localStorage.setItem('isPushed',false);
// Your Code to be executed when entering to back page.
}
}
ionViewWillEnter() always gets executed when the particular page is navigated. So, my idea here is just to detect if it is navigated from a next page to a back page. Hope this helps. :)
NOTE : I have not handled all the conditions related to this. That you have to work it out. This is just an idea of logic to use.