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Questions tagged [angular2-changedetection]

473 questions
832
votes
20 answers

How to detect when an @Input() value changes in Angular?

I have a parent component (CategoryComponent), a child component (videoListComponent) and an ApiService. I have most of this working fine i.e. each component can access the json api and get its relevant data via observables. Currently video list…
Jon Catmull
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557
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31 answers

ExpressionChangedAfterItHasBeenCheckedError Explained

Please explain to me why I keep getting this error: ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Obviously, I only get it in dev mode, it doesn't happen on my production build, but it's very annoying and…
Kevin LeStarge
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485
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4 answers

Triggering change detection manually in Angular

I'm writing an Angular component that has a property Mode(): string. I would like to be able to set this property programmatically not in response to any event. The problem is that in the absence of a browser event, a template binding {{Mode}}…
jz87
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393
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19 answers

@ViewChild in *ngIf

Question What is the most elegant way to get @ViewChild after corresponding element in template was shown? Below is an example. Also Plunker available. Component.template.html:
sinedsem
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272
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5 answers

What's the difference between markForCheck() and detectChanges()

What is the difference between ChangeDetectorRef.markForCheck() and ChangeDetectorRef.detectChanges()? I only found information on SO as to the difference between NgZone.run(), but not between these two functions. For answers with only a reference…
parliament
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225
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7 answers

What is the Angular equivalent to an AngularJS $watch?

In AngularJS you were able to specify watchers to observe changes in scope variables using the $watch function of the $scope. What is the equivalent of watching for variable changes (in, for example, component variables) in Angular?
Erwin
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223
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6 answers

How to force a component's re-rendering in Angular 2?

How to force a component's re-rendering in Angular 2? For debug purposes working with Redux i'd like to force a component to re-render it's view, is that possible?
born2net
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87
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11 answers

ngIf - Expression has changed after it was checked

I have a simple scenario, but just can't get it working! In my view I display some text in a box with limited height. The text is being fetched from the server, so the view updates when the text comes in. Now I have an 'expand' button that has a…
naomi
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70
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6 answers

Trigger update of component view from service - No Provider for ChangeDetectorRef

I would like to udpate my application view, triggered by events from service. One of my services injects the ChangeDetectorRef. Compilation works, but I am getting an error in the browser when the App is bootstrapped: No provider for…
EricJ
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11 answers

Angular2: *ngFor does not update when array is updated

I have an array of objects (arr). In one of my component's inputs, in the (change) method, I modify the attribute of one of the objects but in the view (*ngFor) nothing changes. I read that Angular’s change detection doesn't check the contents of…
Roland Rácz
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42
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5 answers

Angular2 - Expression has changed after it was checked - Binding to div width with resize events

I have done some reading and investigation on this error, but not sure what the correct answer is for my situation. I understand that in dev mode, change detection runs twice, but I am reluctant to use enableProdMode() to mask the issue. Here is a…
Anthony Day
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39
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2 answers

Angular2 zone.run() vs ChangeDetectorRef.detectChanges()

Say I have a function noificationHandler() in my service.ts that is outside of angular's context. noificationHandler() is invoked by a third party and noificationHandler() basically consumes an array and emits the array to components which have…
Ajey
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33
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2 answers

Why do I need to call detectChanges() with the default change detection strategy?

I am working on an Angular 4 app, but I am having a problem inasmuch as I am having to call this.changeDetectorRef.detectChanges(); to update the view when the model changes. For example, I have this code which is for…
serlingpa
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2 answers

Angular 2 Component listen to change in service

I've a simple question about change detection. I have a component and a (global) service with a boolean inside. How can I make the component listen to that boolean and execute a function if that boolean changes? Thanks!
Han Che
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5 answers

How to re-trigger all pure pipes on all component tree in Angular 2

I have pure pipe TranslatePipe that translates phrases using LocaleService that has locale$: Observable current locale. I also have ChangeDetectionStrategy.OnPush enabled for all my components including AppComponent. Now, how can I reload…
Ivan Zyranau
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