Get data async before a `Page` gets rendered

For anyone crawling Stackoverflow about restricting page access when using Ionic 2, it looks like Ionic's recommended lifecycle event to tap into is ionViewCanEnter.

From the docs:

ionViewCanEnter Runs before the view can enter. This can be used as a sort of "guard" in authenticated views where you need to check permissions before the view can enter.

http://ionicframework.com/docs/v2/api/navigation/NavController/

I'm not sure if this is the official way to do it, but I use the Loading component for situations like this one. You can find more information in Ionic API Docs.

The page .ts file would look like this:

import {Component} from '@angular/core';import {Loading, NavController} from 'ionic-angular';@Component({  templateUrl:"page1.html"})export class Page1 {  // Loading component  loading : any;  // Information to obtain from server  comments: string = '';  constructor(nav: NavController) {    this.nav = nav;  }  onPageWillEnter() {    // Starts the process     this.showLoading();  }  private showLoading() {    this.loading = Loading.create({      content: "Please wait..."    });    // Show the loading page    this.nav.present(this.loading);    // Get the Async information     this.getAsyncData();  }  private getAsyncData() {    // this simulates an async method like    // this._service.getComments().then((data) => {     //     this.comments = data);    //     this.hideLoading();    // });    setTimeout(() => {      // This would be the part of the code inside the => {...}      this.comments = "Data retrieved from server";      // Hide the loading page      this.hideLoading();    }, 5000);  }  private hideLoading(){    // Hide the loading component    this.loading.dismiss();  }}

The code is very simple so it doesn't need further details, the idea is to define a loading so we can show it, then try to obtain the information, and as soon as we get that data, we can hide it calling the this.loading.dismiss() method.

You can find a working plunker here (using beta.9)

If you only navigate to that page from one location, couldn't you simply load the data before navigating and using the NavParams to pass the data?

I am using this structure for a Profile page, from a certain index page I click on a user, and then retrieve his profile before visiting his profile. You can show a nice Loading while this is happening.

let self=this;this.profileSvc.getProfile(id).then(profile => {    self.nav.push(Profile, {profile:profile});});

Now in the Profile page you can use the NavParams to initialize your page.

export class Profile {    profile:any;    constructor(private params:NavParams) {        if(params.get('profile')) {            this.profile = params.get('profile');        } else {            this.profile = this.me;        }    }