Angular 2 @ViewChild annotation returns undefined
I am trying to learn Angular 2.
I would like to access to a child component from a parent component using the @ViewChild Annotation.
Here some lines of code:
In BodyContent.ts I have:
import { ViewChild, Component, Injectable } from 'angular2/core';
import { FilterTiles } from '../Components/FilterTiles/FilterTiles';
@Component({
selector: 'ico-body-content',
templateUrl: 'App/Pages/Filters/BodyContent/BodyContent.html',
directives: [FilterTiles]
})
export class BodyContent {
@ViewChild(FilterTiles) ft: FilterTiles;
public onClickSidebar(clickedElement: string) {
console.log(this.ft);
var startingFilter = {
title: 'cognomi',
values: [ 'griffin', 'simpson' ]
}
this.ft.tiles.push(startingFilter);
}
}
while in FilterTiles.ts:
import { Component } from 'angular2/core';
@Component({
selector: 'ico-filter-tiles',
templateUrl: 'App/Pages/Filters/Components/FilterTiles/FilterTiles.html'
})
export class FilterTiles {
public tiles = [];
public constructor(){};
}
Finally here the templates (as suggested in comments):
BodyContent.html
<div (click)="onClickSidebar()" class="row" style="height:200px; background-color:red;">
<ico-filter-tiles></ico-filter-tiles>
</div>
FilterTiles.html
<h1>Tiles loaded</h1>
<div *ngFor="#tile of tiles" class="col-md-4">
... stuff ...
</div>
FilterTiles.html template is correctly loaded into ico-filter-tiles tag (indeed I am able to see the header).
Note: the BodyContent class is injected inside another template (Body) using DynamicComponetLoader: dcl.loadAsRoot(BodyContent, '#ico-bodyContent', injector):
import { ViewChild, Component, DynamicComponentLoader, Injector } from 'angular2/core';
import { Body } from '../../Layout/Dashboard/Body/Body';
import { BodyContent } from './BodyContent/BodyContent';
@Component({
selector: 'filters',
templateUrl: 'App/Pages/Filters/Filters.html',
directives: [Body, Sidebar, Navbar]
})
export class Filters {
constructor(dcl: DynamicComponentLoader, injector: Injector) {
dcl.loadAsRoot(BodyContent, '#ico-bodyContent', injector);
dcl.loadAsRoot(SidebarContent, '#ico-sidebarContent', injector);
}
}
The problem is that when I try to write ft into the console log, I get undefined, and of course I get an exception when I try to push something inside the "tiles" array: 'no property tiles for "undefined"'.
One more thing: FilterTiles component seems to be correctly loaded, since I'm able to see the html template for it.
Any suggestions?I had a similar issue and thought I'd post in case someone else made the same mistake. First, one thing to consider is AfterViewInit; you need to wait for the view to be initialized before you can access your @ViewChild. However, my @ViewChild was still returning null. The problem was my *ngIf. The *ngIf directive was killing my controls component so I couldn't reference it. import { Component, ViewChild, OnInit, AfterViewInit } from 'angular2/core'; import { ControlsComponent } from './controls/controls.component'; import { SlideshowComponent } from './slideshow/slideshow.component'; @Component({ selector: 'app', template: ` <controls *ngIf="controlsOn"></controls> <slideshow (mousemove)="onMouseMove()"></slideshow> `, directives: [SlideshowComponent, ControlsComponent], }) export class AppComponent { @ViewChild(ControlsComponent) controls: ControlsComponent; controlsOn: boolean = false; ngOnInit() { console.log('on init', this.controls); // this returns undefined } ngAfterViewInit() { console.log('on after view init', this.controls); // this returns null } onMouseMove(event) { this.controls.show(); // throws an error because controls is null } } EDIT As mentioned by @Ashg below, a solution is to use @ViewChildren instead of @ViewChild.
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