Observer

An observer is a design pattern used in programming where an object (the observer) is notified of changes or events in another object (the subject). When the subject's state changes, it automatically informs all registered observers, allowing them to update or react accordingly. This pattern promotes loose coupling, making systems more flexible and maintainable, as observers can be added or removed without altering the subject's core code. It is commonly used in user interfaces, event handling, and situations requiring real-time updates.