The Core Purpose of Effects

Effects exist mainly to handle output that data binding cannot cover. The Angular documentation lists logging, canvas painting, and custom DOM manipulation as typical scenarios. Since data binding remains the standard mechanism for presenting information to users, it makes sense that Effects are described as occasionally necessary rather than essential.

Chau Tran's Angular Three library serves as a strong illustration of canvas-related work, bridging Angular with Three.js. For custom DOM behavior, think of situations where template syntax falls short — displaying a SnackBar through an imperative API such as the one provided by Angular Material.

Understanding Auto-Tracking

Angular relies on implicit tracking for both computed and effects. Consider this scenario: the effect will monitor the error Signal even when that Signal is only referenced inside the logError method called by the effect, not directly within the effect function itself.

effect(() => {
  this.logError();
});
:
logError(): void {
  const error = this.error();
  if (error) {
    console.error(error);
  }
}

This behavior highlights that the current Effects implementation targets rendering scenarios. Any Signal accessed during rendering gets tracked, and modifying it triggers another render pass. Alex Rickabaugh has elaborated on this design choice in a GitHub issue discussion.

When Effects Should Be Avoided

The documentation explicitly advises against using Effects for state propagation. Problems like circular updates can emerge. Beyond that, auto-tracking can produce code that becomes increasingly difficult to maintain over time — a point also raised in the referenced GitHub conversation.

Effects push code toward imperative patterns and away from the declarative style that reactive programming favors. For guidance on writing more declarative code, Mike F. Pearson — the author behind StateAdapt — offers useful resources.

Another consideration: Signals guarantee glitch-free behavior. Changing a Signal multiple times within the same stack frame results in only the final value being observed. This property suits rendering well but indicates that Signals are not ideal for modeling event streams.

Effects Behind the Scenes

Although not documented, Effects power several reactive helpers under the hood. Angular's toObservable, rxMethod from NGRX Signal Store, and numerous utilities in ngxtension by Chau Tran and Enea Jahollari all depend on Effects internally.

This point will resurface again near the conclusion.

Responding to Signal Updates

After covering appropriate and inappropriate Effect usage, a natural question arises: what is the right way to respond when Signals change? Multiple strategies exist:

1) Use computed or the Resource API for state derivation
2) Listen for the event that caused the Signal change
3) Leverage RxJS
4) Employ reactive helper utilities

The computed approach works when you can derive the desired value synchronously from existing Signals. For asynchronous derivation, the Resource API is available.

For option 2, instead of watching the Signal itself, respond to the underlying event:

When (Not) to use Effects in Angular — and what to do instead — figure 1

Reacting to the source event sidesteps complications like auto-tracking side effects and circular update risks.

Option 3 involves using RxJS either as a replacement or complement to Signals. Angular's interop functions — toObservable and toSignal — bridge the two paradigms. RxJS enables a fully reactive pipeline from user interaction through to output. The flattening operators in RxJS, including switchMap, offer protection against overlapping requests and race conditions. Jan-Niklas Wortmann explored these topics during his ng-conf 2024 presentation on reactivity in Angular applications.

Regarding option 4, rxMethod in NGRX Signal Store and deriveAsync from ngxtension are notable reactive helpers. A method configured with rxMethod accepts a Signal and connects it to an RxJS pipeline:

this.store.rxLoad(this.id);

Here is a minimal Signal Store implementation with rxLoad:

export const DessertDetailStore = signalStore(
    { providedIn: 'root' },
    withState({
        dessert: initDessert,
        loading: false
    }),
    withMethods((
        store,
        dessertService = inject(DessertService)
    ) => ({
        rxLoad: rxMethod<number>(pipe(
            tap(() => patchState(store, { loading: true })),
            switchMap((id) => dessertService.findById(id)),
            tap((dessert) => patchState(store, { dessert, loading: false })),
        )),
    }))
);

Error handling was intentionally omitted from this straightforward example.

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When (Not) to use Effects in Angular — and what to do instead — figure 2

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Evaluating explicitEffect

The explicitEffect helper has generated considerable discussion, including within the GitHub issue referenced earlier. An implementation exists in ngxtension. Essentially, it merges effect with untracked to limit tracking to a specified set of Signals:

explicitEffect(this.id, (id) => {
  this.store.load(id);
});

In this example, only the id Signal gets tracked. An explicit Effect offers a straightforward way to control auto-tracking when using Effects beyond rendering. However, it does not solve the other fundamental issues with such usage. Cyclic updates remain possible, and the code can still become difficult to follow. Moreover, the imperative nature of this approach conflicts with the declarative, event-driven style characteristic of reactive programming.

Those committed to the reactive paradigm will likely skip explicitEffect altogether. RxJS, helper utilities like rxMethod, various declarative tools in ngxtension, or the Resource API will serve better. This is also the recommended path. If you still choose to use this kind of effect, you and your team should fully understand the trade-offs.

Wrapping Up

Effects primarily handle output that data binding cannot manage — logging, canvas rendering, or custom DOM behavior like displaying a SnackBar through an imperative API similar to Angular Material's. When responding to Signal changes, prefer computed for synchronous derivation or the Resource API for async scenarios. Alternatively, listen for the originating events, use RxJS, or rely on reactive helpers to build a complete end-to-end reactive chain.