javascript - Angular2 calling custom function after ngSwitch new view is created

Question

I am creating a small app using Angular2+Ionic2. In this app I want initialise google-map into view segment when user switch to the map-segment using ion-segment

Following is the sample code structure:

<ion-navbar *navbar class="hide-navbar">
    <ion-segment [(ngModel)]="homeSegment">
        <ion-segment-button value="list">
            List..
        </ion-segment-button>
        <ion-segment-button value="map" >
            Map
        </ion-segment-button>
    </ion-segment>
</ion-navbar>
<ion-content>
    <div [ngSwitch]="homeSegment" >

        <div *ngSwitchWhen="'map'">
            <div id="googleMap"></div>
        </div>

        <ion-list *ngSwitchWhen="'list'">
           Listing
        </ion-list>
    </div>
</ion-content>

I have tried by providing click listener for ion-segment-button, but that doesn't worked out. Before div with id="googleMap" is appended to DOM, functionality for adding map gets triggered, and which result a undefined error.

So, how we can understand when new elements are loaded when an ngSwitch happens? Whats the best way to do it?

update (adding js code)

import {Page, NavController} from 'ionic-angular';
import {DataServiceManager} from '../../services/dataServicesManager';

@Page({
  templateUrl: 'build/pages/listFob/listFob.html'
})
export class ListFob {
    static get parameters(){
        return [[NavController],[DataServiceManager]];
    }
    onPageWillEnter(){
        this.fetchFobs();
    }
    ngOnInit(){
        console.log("on init");
        console.log(this.homeSegment);
    }
    ngAfterContentChecked() {
        console.log("content checked")
    }
    constructor(nav, dataServiceManager){
        this.nav = nav;
        this.dataServiceManager = dataServiceManager;
        this.homeSegment = "list";
    }
    loadMap(){
        console.log(document.getElementById("googleMapAllFobs"));
        // TODO: load map functionality
    }
}

Error message coming while adding Directive

./app/directives/switch-segment.js
Module build failed: SyntaxError: /Users/Piccaza/ionic-projects/learning/fob/app/directives/switch-segment.js: Unexpected token (8:27)
   6 | })
   7 | export class SwitchSegment {
>  8 |     @Output() switchSegment: EventEmitter = new EventEmitter();
     |                            ^
   9 |     ngOnInit() {
  10 |         console.log("Directive triggered!");
  11 |         this.onCreate.emit('dummy');
    at Parser.pp.raise (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:1378:13)
    at Parser.pp.unexpected (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2817:8)
    at Parser.pp.expect (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2811:33)
    at Parser.pp.parseMethod (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:1091:8)
    at Parser.pp.parseClassMethod (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2495:8)
    at Parser.pp.parseClassBody (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2456:10)
    at Parser.pp.parseClass (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2339:8)
    at Parser.pp.parseStatement (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:1813:19)
    at Parser.pp.parseExportDeclaration (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2578:15)
    at Parser.pp.parseExport (/Users/Piccaza/ionic-projects/learning/fob/node_modules/babylon/index.js:2566:29)
 @ ./app/pages/listFob/listFob.js 16:21-63 (CLI v2.0.0-beta.19)

Your system information:

Cordova CLI: Not installed
Ionic Version: 2.0.0-beta.3
Ionic CLI Version: 2.0.0-beta.19
Ionic App Lib Version: 2.0.0-beta.9
ios-deploy version: 1.8.5 
ios-sim version: 5.0.6 
OS: Mac OS X El Capitan
Node Version: v5.3.0
Xcode version: Xcode 7.2.1 Build version 7C1002 

Answer 1

There is no built-in support of calling a function when ngSwitch adds/removes elements.

I would create a directive that calls the function when created (for example in ngOnInit()) or emits an event where an event handler can be bound to, and apply it to the component that is added when the ngSwitch branch is enabled.

If ngSwitch adds a component you can implement it in this component as well (depends on your requirements)

update

    <ion-list (onCreate)="doSomething()" *ngSwitchCase="'list'">
       Listing
    </ion-list>

@Directive(selector: '[onCreate]')
export class OnCreate implements OnInit {
  @Output() onCreate:EventEmitter = new EventEmitter();

  ngOnInit() {
    this.onCreate.emit('dummy');
  }
}

Plunker example