MVC with Flex

Prabhu Sunderaraman, Software Mentor, DuraSoft

Flex is one of the really rich mechanisms for creating Rich Internet

Applications, which  has grown very rapidly over last few years.  Plenty of

applications that have charts and reports are implemented using Flex.

Working with Flex can get really clumsy if you don't follow a proper design

to layout various entities in your applications. The code in MXML files tend to

get too crowded and unmanageable after sometime. Making changes and

incorporating new functionalities becomes tedious and time consuming. The best

way to handle this issue is to remove the ActionScript code out of the MXML

files. The evergreen Model-View-Controller (MVC) pattern can be used to create

maintainable Flex applications. MVC pattern in Flex focuses on separating the

ActionScript code and the UI elements used in MXML. The MVC pattern can either

be hand-tossed or implemented using standard frameworks in your  applications.

Hand tossing the MVC pattern has its own pros and cons. It gives complete

control of the flow in the application, but can get very difficult as the

application grows. There are a number of Flex MVC  implementations available

that can be used in your applications. These frameworks bring in a discipline in

the way Flex applications are created. A list of some of the well-known Flex MVC

frameworks are given below.

Each framework has its own advantages and disadvantages. Based on the

complexity of the application,  one of these frameworks can be chosen to

implement MVC.

Pure MVC: http://puremvc.org. Pure MVC is an open source

implementation of MVC pattern and one of the widely used. It provides

traditional set of model, view and controller classes. It is built using the

popular command, singleton, Façade and Observer design patterns.

Cairngorm  http://opensource.adobe .com/wiki/ display/cairngorm/ Cairngorm.

Cairngorm is Adobe's open source lightweight MVC implementation. It uses the

popular J2EE patterns like ServiceLocator, BusinessDelegate in its

implementation. Similar to the Pure-MVC framework, Cairngorm also has its own

set of controller and command classes.

Mate: http://mate.asfusion.com/. Mate is the MVC framework based on

events and dependency injection. It provides facilities to handle events in a

customized manner. The data that is processed or fetched from different sources

can be injected into different parts of the application.