Computed signal
A computed signal is a read-only reactive value derived from other signals and recalculated when its dependencies change.
Modern Angular
The Angular computed function creates a derived read-only signal whose value is recalculated when the signals it reads change.
- How it is used
- Derives values from one or more signals while keeping data flow automatic and readable.
- How deep it goes
- Defines callback-based derivation, dependency tracking, automatic recalculation, and stored results for unchanged dependencies.
- Examples
- Uses doubled counts, sums of multiple signals, and recalculation logging to demonstrate derived values and caching.
- What you can do after
- Apply it via Angular’s computed function to build read-only derived signals without manual synchronization code.
Pro Angular 16
The computed function is an Angular API function that creates a read-only signal from a derivation function whose signal reads establish its dependencies.
- How it is used
- Derives display-ready values from application state while avoiding recalculation of unchanged values.
- How deep it goes
- Explains read-only creation, dependency tracking, lazy memoized recomputation, and a non-signal dependency pitfall through component examples.
- Examples
- Uses product categories, category filtering, pagination, product counts, CSS classes, and latest-message display.
- What you can do after
- Apply it via Angular’s `computed` function to derive repository and component values that refresh when their signal dependencies change.
Related concepts
- signaluses · A signal is an observable value, event, or pattern that conveys information about a condition, state, or phenomenon.
- paginationused by · Pagination is the technique of dividing a collection or result set into bounded portions that can be retrieved or displayed separately.
- WritableSignal<T>contrasts with · WritableSignal<T> is an Angular signal whose stored value can be changed through writable operations.
- dependencyuses · A software dependency is a component, resource, or prerequisite on which another software component or operation relies to function or proceed.
These guides are generated from the text of Manning books by Manning's knowledge graph and link to the sections they draw on. The full books are available on liveBook and at manning.com.