Why does Angular 5 throw this error?
AppComponent.html:2 ERROR TypeError: Cannot read property 'forEach' of undefined
I am working on a proof-of-concept for Angular animations and I'm using the code directly from the site. My component looks like this:
import { Component, OnInit } from '@angular/core';
import { trigger, state, style, transition, animate, keyframes } from '@angular/animations';
@Component({
selector: 'app-obj-list',
templateUrl: './obj-list.component.html',
styleUrls: ['./obj-list.component.css'],
animations: [
trigger('myAwesomeAnimation', [
state('small', style({
transform: 'scale(1)',
})),
state('large', style({
transform: 'scale(1.2)',
})),
]),
transition('small => large', animate('100ms ease-in'))
]
})
export class ObjListComponent implements OnInit {
state = 'small';
constructor() { }
animateMe() {
this.state = (this.state === 'small' ? 'large' : 'small');
}
ngOnInit() {
}
}
The line of code that the error references is just the tag to include my component: <app-obj-list></app-obj-list>
I've narrowed it down to the line in the above file: transition('small => large', animate('100ms ease-in'))
When I remove that line, the error goes away. When I leave it in, I get the error:
AppComponent.html:2 ERROR TypeError: Cannot read property 'forEach' of undefined
at new AnimationTrigger (browser.js:3017)
at buildTrigger (browser.js:3005)
at InjectableAnimationEngine.AnimationEngine.registerTrigger (browser.js:5504)
at eval (animations.js:291)
at Array.forEach (<anonymous>)
at AnimationRendererFactory.createRenderer (animations.js:290)
at DebugRendererFactory2.createRenderer (core.js:15075)
at createComponentView (core.js:13633)
at callWithDebugContext (core.js:15041)
at Object.debugCreateComponentView [as createComponentView] (core.js:14370)
My app.module has the BrowserAnimationsModule so that shouldn't be the issue:
import { BrowserModule } from '@angular/platform-browser';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import { ObjListComponent } from './obj-list/obj-list.component';
@NgModule({
declarations: [
AppComponent,
ObjListComponent
],
imports: [
BrowserModule,
BrowserAnimationsModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }
I'm trying to follow the code on the angular site as closely as I can. Can someone tell me what I'm forgetting? Is there an import I'm forgetting? Is there a package I need to download? I'm new to Angular and Angular animations and I can't seem to figure this out.
If you look closely at the tutorial, the "transition" property of the animation needs to be inside of the array of "trigger":
animations: [
trigger('myAwesomeAnimation', [
state('small', style({
transform: 'scale(1)',
})),
state('large', style({
transform: 'scale(1.2)',
})),
transition('small => large', animate('100ms ease-in'))
]) // close the array after the transition
]
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