Computed signals for derived values in Angular - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a computed signal in Angular?

A computed signal is a special kind of signal that automatically calculates its value based on other signals. It updates whenever its dependencies change.

beginner

How do computed signals help in managing derived state?

They keep derived values in sync automatically without manual updates, reducing bugs and making code easier to read.

beginner

Which Angular function creates a computed signal?

The function is called computed(). You pass a function that returns the derived value.

intermediate

What happens when a signal used inside a computed signal changes?

The computed signal automatically recalculates its value and updates any parts of the app that use it.

advanced

Can computed signals cause infinite loops? How to avoid them?

Yes, if a computed signal indirectly depends on itself. To avoid this, ensure dependencies form a clear, acyclic graph.

What does the Angular computed() function do?

A Creates a signal that derives its value from other signals

B Creates a signal that stores user input

C Creates a signal that never changes

D Creates a signal that triggers HTTP requests

The computed() function creates a signal whose value depends on other signals and updates automatically.

If a signal used inside a computed signal changes, what happens?

A The signal resets to default

B The computed signal recalculates its value

C The app crashes

D Nothing changes automatically

Computed signals listen to their dependencies and recalculate when those signals change.

Which of these is a benefit of using computed signals?

A Manual updates of derived values

B Slower app performance

C Automatic syncing of derived values

D More complex code

Computed signals automatically keep derived values in sync, making code simpler and less error-prone.

What should you avoid to prevent infinite loops with computed signals?

A Having a computed signal depend on itself directly or indirectly

B Using signals only once

C Using signals in templates

D Using signals with HTTP calls

A computed signal must not depend on itself, or it will cause infinite recalculations.

Which Angular concept is closely related to computed signals?

A Directives

B Forms

C Routing

D Signals and reactivity

Computed signals are part of Angular's reactive signals system.

Explain how computed signals work in Angular and why they are useful.

Think about how a calculator updates its display when you change inputs.

Describe a scenario where using a computed signal prevents bugs compared to manual updates.

Imagine forgetting to update a total price after changing quantity.