Observer Pattern - sivakrsna/DesignPatterns GitHub Wiki

The Observer Pattern defines a one-to-many dependency between objects so that when one object changes state, all of its dependents are notified and updated automatically.

• 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.

The Observer Pattern defines a one-to-many relationship between a set of objects. When the state of one object changes, all of its dependents are notified.

The Observer pattern addresses the following problems:

• A one-to-many dependency between objects should be defined without making the objects tightly coupled.
• It should be ensured that when one object changes state an open-ended number of dependent objects are updated automatically.
• It should be possible that one object can notify an open-ended number of other objects.