MVC vs. Observer Pattern

问题:

I've recently asked a question on StackoverFlow about the MVC: Can the MVC Design Pattern / Architectural pattern be used in Desktop Application Development?

Based on the answer provided I started research on how this would be implemented in a Windows form Application. I came upon the following CodeProject article: http://www.codeproject.com/KB/cs/model_view_controller.aspx

In the comments below the article, certain users argue that (although this is a good article) it is actually the observer pattern. First, but less important, question is does anyone agree or disagree with that and why?

Regarding the second and more important question: I'm trying to build a small task list program in .NET. It will be very tiny and hopefully fast. In general, what would be a better architecture for such a project? The Observer Pattern or the MVC Pattern? Or another pattern?

Thank you

回答1:

(The article is not an example of MVC AFAIK for the simple reason that there is no controller.. it is more close to .net data binding if you ask me.)
MVC is not the Observer pattern. MVC is concerned with separation of concerns. The Model, the View and the Controller all do one job and trust the others to do theirs. In a way, the Controller 'directs' the view and tells it how to react to a change (Pure MVC). The controller also interacts with the model appropriately (whose responsibility is to encapsulate data and enforce constraints/rules). In MVC, the controller is the starting point for all activities - user input is received by the controller first.. However there are variants like MVP, where the user is input is received by the view first and then pushed/synched with the presenter.

The Observer pattern is where you want to watch another object for a change in state. So you could say .net events follow the observer pattern

If its really tiny, forget about patterns and just code it up without worrying about the architecture... Follow the heuristics/principles of good design

• http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod
• http://mmiika.wordpress.com/oo-design-principles/

If you run into design issues or it starts to get all messy, then bring in the pattern battalions.

回答2:

usually the model in an mvc (http://en.wikipedia.org/wiki/Model-view-controller) is an observable/subject (http://en.wikipedia.org/wiki/Observer_pattern#Subject), while the views are observers (http://en.wikipedia.org/wiki/Observer_pattern#Observer). also see: mvc in http://webcourse.cs.technion.ac.il/234321/Winter2005-2006/ho/WCFiles/08-Design-Patterns.ppt

回答3:

I would agree that the article is not MVC. Its more of an implementation of observer pattern. Observer pattern in .NET can be implemented by using events, which was the case of the article.

MVC requires a controller class that controls what action to execute upon a request made from either the model, or the view. Applying MVC is a very good programming practice as it greatly promotes separation of concern. You will have a cleaner, more extensible, and more testable app with mvc. Another point to note, you can still apply observer pattern to an MVC app. They will not contradict each other.

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To answer your second question: which pattern is the best? I think the way you approach software development is rather wrong. You shouldn't worry too much about those things yet, not until you've hit a problem. e.g. If this object changes state I need these other objects to react to it, hence I would implement an observer pattern.

If I were you I would start on the model side first, and then takes things from there.