The observer pattern is a software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods. It is mainly used to implement distributed event handling systems. The Observer pattern is also a key part in the familiar Model View Controller (MVC) architectural pattern. In fact the observer pattern was first implemented in Smalltalk's MVC based user interface framework. The observer pattern is implemented in numerous programming libraries and systems, including almost all GUI toolkits.
Related patterns: Publish–subscribe pattern, mediator, singleton.
Read more about Observer Pattern: Example
Famous quotes containing the words observer and/or pattern:
“History, as an entirety, could only exist in the eyes of an observer outside it and outside the world. History only exists, in the final analysis, for God.”
—Albert Camus (1913–1960)
“Man is eminently a storyteller. His search for a purpose, a cause, an ideal, a mission and the like is largely a search for a plot and a pattern in the development of his life story—a story that is basically without meaning or pattern.”
—Eric Hoffer (1902–1983)