Thursday, July 5, 2007

Model View Presenter

For those of you that did not come to the last Perl User Group meeting, you missed a great presentation which prompted a wonderful discussion on the Model-View-Presenter Pattern (MVP). Primarily being a J2EE developer and with many years of experience with the Struts Framework, I am very familiar with the Model-View-Controller (MVC). I was very interested, however, in this MVP pattern. This is mostly due to the thick client application development that I have been doing lately.

During the meeting, a lot of questions were raised regarding this pattern, and Jason Porrit was very patient with all of us (touche'). After the meeting, I decided to do a little more investigation, and found the following:

Martin Fowler Retires Model View Presenter Pattern

Yes. Believe it or not, this pattern has been retired by Martin Fowler. Well, I don't know if retired is the correct 'r'-word. Maybe it should say 'R'efactored instead. He has split up the pattern into the Supervising Controller and the Passive View. After reading both of the patterns, they sound very similar in detail and in practice. In the Passive View you put all of the widget population logic into the Presenter. All logic is pushed on the Presenter including the population of text fields or any other widgets available on the View. In the Supervising Controller, you push most of the logic onto the Presenter, but leave some of the logic of populating widgets in the View. Martin states:

"...the essence of a good Supervising Controller is to do as little as possible. Let the view handle as much as possible and only step in when there's more complex logic involved."

Atomic Object Presenter First
On a related note, Atomic Object also has their own variation of the MVP Design pattern called Presenter First (PF). After reading an article from Better Software magazine (referenced from their PF resources), I find this design pattern very attractive as well. What most attracts me is the concept of linking different PF triads in order to orchestrate behavior and a process. Please refer tot he Better Software article for more information on this.

Overall, I owe a big thanks to Jason for inspiring me to learn more about this design pattern. I look forward to hearing him present in the future.

No comments: