A Gang of Four behavioral design pattern that defines a one-to-many dependency between objects so that when one object, the subject, changes state, every object registered as its observer is notified and updated automatically.
Facts
Core PrincipleDefines a one-to-many dependency between a subject and its observers so that when the subject changes state, all its registered observers are notified automatically. 2 Connections
Associated With
Erich Gamma, Pioneers Erich Gamma co-authored the 1994 Design Patterns book that named and catalogued the Observer pattern among the original 23.
In Field
Sources
1. Wikipedia: Design Patterns (book)
Wikimedia FoundationLead section, first sentenceQuote, Lead section, first sentence
Design Patterns: Elements of Reusable Object-Oriented Software (1994) is a software engineering book describing software design patterns.
2. Wikipedia: Observer Pattern
Wikimedia FoundationLead section, first sentenceQuote, Lead section, first sentence
the observer pattern is a software design pattern in which an object, called the subject (also known as event source or event stream), maintains a list of its dependents, called observers (also known as event sinks), and automatically notifies them of any state changes
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