Observer

The Observer component provides two interfaces for the classic Observer design pattern. A subject maintains a list of observers and notifies them when something changes. PSL's interfaces are generic, so observers receive the concrete subject type rather than a vague base class.

Design

• SubjectInterface -- The object being watched. It can subscribe(), unsubscribe(), and notify() observers.
• ObserverInterface<T> -- The watcher. Its update() method receives the subject that triggered the notification, fully typed as T.

Usage

The following example demonstrates a complete Subject/Observer implementation, including wiring them together:

@example('other/observer-pattern.php')

See src/Psl/Observer/ for the full API.