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 possibility of interpretation lies in the identity of the observer with the observed. Each material thing has its celestial side; has its translation, through humanity, into the spiritual and necessary sphere, where it plays a part as indestructible as any other.”
—Ralph Waldo Emerson (1803–1882)
“It was her stern necessity: all things
Are of one pattern made; bird, beast, and flower,
Deceive us, seeming to be many things,
And are but one. Beheld far off, they differ
As God and devil; bring them to the mind,
They dull its edge with their monotony.”
—Ralph Waldo Emerson (1803–1882)