Observer

Definitions

1. A behavioral design pattern in which an object (the subject) maintains a list of dependents (observers) and automatically notifies them of state changes, decoupling the producer of events from the consumers that react to them.

   In plain English: A pattern where interested parties sign up to be automatically told whenever something they care about changes.

   Example: "The shopping cart is the subject and the price display, tax calculator, and analytics tracker are all observers — update the cart and they all react."

Related Terms

• Iterator Pattern
• Lazy Initialization
• Message Bus
• Model-View-Controller
• Plugin Architecture
• Presenter
• Provider Pattern
• Push Model
• Service Object