import { Component } from '@angular/core';
import { HomePage } from './home.page';

@Component({
  template: `<ion-nav [root]="rootPage"></ion-nav>`
})
export class AppComponent {

  rootPage = HomePage;

}


/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/
import { NgModule } from '@angular/core';
import { IonicApp, IonicModule } from 'ionic-angular';

import { AppComponent } from './app.component';
import { HomePage } from './home.page';
import { NextPage } from './next.page';

@NgModule({
  imports: [ IonicModule.forRoot(AppComponent) ],
  declarations: [ AppComponent, HomePage, NextPage ],
  entryComponents: [ HomePage,NextPage ],
  bootstrap: [ IonicApp ]
})
export class AppModule { }


/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app.module';

const platform = platformBrowserDynamic();
platform.bootstrapModule(AppModule);


/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/
<!DOCTYPE html>
<html>
  <head>
    <title>Ionic 2 QuickStart</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <!-- 1. Load libraries -->
     <!-- Polyfill(s) for older browsers -->
    <script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script>

    <script src="https://unpkg.com/zone.js@0.6.21?main=browser"></script>
    <script src="https://unpkg.com/systemjs@0.19.40/dist/system.src.js"></script>

    <!-- 2. Configure SystemJS -->
    <script src="systemjs.config.js"></script>
    <link href="https://unpkg.com/ionic-angular@2.0.0-rc.6/css/ionic.css" rel="stylesheet">
  </head>

  <!-- 3. Display the application -->
  <body>
    <ion-app></ion-app>
    <script>
      System.import('app').catch(function(err){ console.error(err); });
    </script>
  </body>
</html>


<!-- 
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
-->
### Ionic 2 - Make API Call Before Loading Page

Basic Ionic 2 plunk based on the Angular QuickStart plunk.
trying to answer this question from the Ionic Forum

We use `ionViewCanEnter` as a guard to load data and only if it resolves do we go forward

[Make API Call Before Loading Page](https://forum.ionicframework.com/t/make-api-call-before-page-load/55877/7)

###CheckOut Video on YouTube
https://youtu.be/ZWYhR4Qo0PE
/**
 * PLUNKER VERSION
 * (based on systemjs.config.js in angular.io)
 * System configuration for Angular samples
 * Adjust as necessary for your application needs.
 */
(function (global) {
  System.config({
    // DEMO ONLY! REAL CODE SHOULD NOT TRANSPILE IN THE BROWSER
    transpiler: 'ts',
    typescriptOptions: {
      tsconfig: true
    },
    meta: {
      'typescript': {
        "exports": "ts"
      }
    },
    paths: {
      // paths serve as alias
      'npm:': 'https://unpkg.com/'
    },
    // map tells the System loader where to look for things
    map: {
      // our app is within the app folder
      app: 'app',

      // angular bundles
      '@angular/core': 'npm:@angular/core@2.2.1/bundles/core.umd.js',
      '@angular/common': 'npm:@angular/common@2.2.1/bundles/common.umd.js',
      '@angular/compiler': 'npm:@angular/compiler@2.2.1/bundles/compiler.umd.js',
      '@angular/platform-browser': 'npm:@angular/platform-browser@2.2.1/bundles/platform-browser.umd.js',
      '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic@2.2.1/bundles/platform-browser-dynamic.umd.js',
      '@angular/http': 'npm:@angular/http@2.2.1/bundles/http.umd.js',
      '@angular/forms': 'npm:@angular/forms@2.2.1/bundles/forms.umd.js',
  
      'ionic-angular': 'npm:ionic-angular@2.0.0-rc.6',
      'rxjs': 'npm:rxjs@5.0.0-beta.12',
      'ts': 'npm:plugin-typescript@5.2.7/lib/plugin.js',
      'typescript': 'npm:typescript@2.0.7/lib/typescript.js',

    },
    // packages tells the System loader how to load when no filename and/or no extension
    packages: {
      app: {
        main: './main.ts',
        defaultExtension: 'ts'
      },
      rxjs: {
        defaultExtension: 'js'
      },
      'ionic-angular': {
        main: './umd/index.js',
        defaultExtension: 'js'
      }
    }
  });
})(this);


/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/
{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": true,
    "suppressImplicitAnyIndexErrors": true
  }
}
import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { NextPage } from './next.page'

@Component({
  selector: 'page-home',
  templateUrl: 'app/home.page.html'
})
export class HomePage {

  appName = 'Ionic App';

  constructor(public navController: NavController ) { 
    
  }
  
    
  nextPageWithError() {
    this.navController.push(NextPage, {fail:true}).catch(()=>{
      console.log("Page didnt load")
    })
  }
  
  nextPage() {
    this.navController.push(NextPage).catch(()=>{
      console.log("Page didnt load")
    })
  }
}

<ion-header>
  <ion-navbar>
    <ion-title>{{ appName }}</ion-title>
  </ion-navbar>
</ion-header>

<ion-content padding>
  Welcome to this <ion-icon name="ionic"></ion-icon> <b>Ionic 2 app</b>
  <div>
  <button ion-button (click)="nextPage()" >Next Page</button>
  <button ion-button (click)="nextPageWithError()" >Should Not Load Next Page</button>
  </div>
</ion-content>
import { Component } from '@angular/core';
import { Http } from '@angular/http';
import { NavController, NavParams } from 'ionic-angular';

import { Observable } from 'rxjs';
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/map';
 
@Component({
  selector: 'page-next',
  templateUrl: 'app/next.page.html'
})
export class NextPage {
 http
 userList
 
  constructor (private http: Http,  private params: NavParams) {
    console.log("in constructor")
    this.http = http
  }
  
  ionViewCanEnter() {
    console.log("in ionViewCanEnter")
    
    return new Promise((resolve, reject) => {    
      if (this.params.get('fail')) {
        reject(true)
      } else {
        this.http.get('https://randomuser.me/api/?results=5')
          .map(res => res.json().results)
          .subscribe(
            (res)=> {
              console.log(res)
              this.userList = res
              resolve(res)
            },
            (err)=>{
              reject(err)
            }
          );
      }
    });
  }
  
  ionViewDidEnter() {
    console.log("in ionViewDidEnter")
  }
 
}
<ion-header>

  <ion-navbar>
    <ion-title>Next Page</ion-title>
  </ion-navbar>

</ion-header>


<ion-content padding>
  IN THE NEXT PAGE
  <!-- lets show the data -->
  <ion-list>
    <ion-item *ngFor="let user of userList">
      <div>{{user.name.first}} &nbsp;{{user.name.last}}</div>
      <p>{{user.email}}</p>
    </ion-item>
  </ion-list>

</ion-content>