Ionic4 navController back with params (callback) - ionic4

Question

Just looking for best practice for sending data from a child route, back up to its parent. For example, if I have a list view and I want to add an item which is complex enough to merit its own page, how do I get that added item back to the list view? Now obviously I could just re-fetch the entire list but that seems kind of silly and not efficient. I found that I can also pass a “callback function” in the ActivatedRoute params when router navigates the AddPage, but that also felt wrong (though I like it better than the first option). It’d be great if I could pass the data back through the nav.back() method, but what is the recommended way to do what I need to do?

Answer 1

pass in a callback when transitioning(it is not working in ionic4)
// callback...
myCallbackFunction = function(_params) {
return new Promise((resolve, reject) => {
resolve();
});
}
// push page...
this.navController.navigateForward(["add-product",{"callback": myCallbackFunction}]);
in the AddProductPage
this.activatedRoute.params.subscribe((data: any) => {
this.callback = data.callback;
console.log("callback "+this.callback)
});
error:-i m getting data in string form(here i m getting callback data in string format)
output:-
callback "function(_params) {
return new Promise((resolve, reject) => {
resolve();
});
"
this.callback(param).then(()=>{
this.navController.pop();
});

Answer 2

I do what Pradeep said, and its working:
Put navCtrl in your constructor parameter:
private navCtrl: NavController,
And somewhere in your code when you want to go back:
let navigationExtras: NavigationExtras = {
state: {
param: "1",
}
};
this.navCtrl.navigateBack(['previouspage'], navigationExtras)
In your previous page constructor:
constructor(
........
private router: Router,
){
if (this.router.getCurrentNavigation().extras.state && this.router.getCurrentNavigation().extras.state.param) {
let param = this.router.getCurrentNavigation().extras.state.param
}
}