Delving Deeper into MVC

Delving Deeper into MVC

Right now, you likely have a basic understanding of what the MVC pattern provides, but for the curious, we’ll explore it a little further.

The GoF (Gang of Four) do not refer to MVC as a design pattern, but rather consider it a set of classes to build a user interface. In their view, it’s actually a variation of three other classical design patterns: the Observer (Publish/Subscribe), Strategy, and Composite patterns. Depending on how MVC has been implemented in a framework, it may also use the Factory and Decorator patterns. I’ve covered some of these patterns in my other free book, JavaScript Design Patterns For Beginners if you would like to read about them further.

As we’ve discussed, Models represent application data, while Views handle what the user is presented on screen. As such, MVC relies on Publish/Subscribe for some of its core communication (something that surprisingly isn’t covered in many articles about the MVC pattern). When a Model is changed it publishes to the rest of the application that it has been updated. The subscriber, generally a Controller, then updates the View accordingly. The observer-viewer nature of this relationship is what facilitates multiple Views being attached to the same Model.

For developers interested in knowing more about the decoupled nature of MVC (once again, depending on the implementation), one of the goals of the pattern is to help define one-to-many relationships between a topic and its observers. When a topic changes, its observers are updated. Views and Controllers have a slightly different relationship. Controllers facilitate Views’ responses to different user input and are an example of the Strategy pattern.