OOP Class13

From IAMMediaWiki Create Change

Inclass Practice Final

http://iam.colum.edu/oop/classsource/class13/ConsoleApplication3.zip

Observer

Observer

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

Observers

http://www.dofactory.com/Patterns/PatternObserver.aspx

Observer is a deisgn pattern that is often used to publish (push) or subcribe (pull) changes in the stae of one object to other intersted object. It encourgaes loose coupling of objects.

The object the get the data often called the subject then notifies the observing objects of the change. The observing object will often repond to the subject.

Here is a real example in c#. In this exmaple a stock (the subject) notifies and investor (the observer) of a change in price.

http://iam.colum.edu/oop/gbrowser.php?file=/classsource/class13/Observer_j.cs

http://iam.colum.edu/oop/classsource/class13/Observer.aspx - source

Observer App

Here's and exmaple of a windows app the uses the observer pattern

http://iam.colum.edu/oop/browser/browser.aspx?f=/classsource/class13/Observer

Here is the start of a web app that does the same

http://iam.colum.edu/oop/classsource/class13/ColorObserver.aspx - source

http://iam.colum.edu/oop/classsource/class13/ColorObserver2.aspx - source

Homework

Build a web page that uses the observer pattern.