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:
“The importance of its hat to a form becomes
More definite. The sweeping brim of the hat
Makes of the form Most Merciful Capitan,
If the observer says so....”
—Wallace Stevens (1879–1955)
“The kind of relatedness to the world may be noble or trivial, but even being related to the basest kind of pattern is immensely preferable to being alone.”
—Erich Fromm (1900–1980)