Rails Architecture : Model , Views and Controllers

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In a Rails application, incoming requests are first sent to a router, which works out where in the application the request should be sent and how the request itself should be parsed. Ultimately, this phase identifies a particular method (called an action in Rails parlance) somewhere in the controller code. The action might look at data in the request itself, it might interact with the model, and it might cause other actions to be invoked. Eventually the action prepares information for the view, which renders something to the user.

The model is responsible for maintaining the state of the application. Sometimes this state is transient, lasting for just a couple of interactions with the user. Sometimes the state is permanent and will be stored outside the application, often in a database.

A model is more than just data; it enforces all the business rules that apply to that data. For example, if a discount shouldn’t be applied to orders of less than $20, the model will enforce the constraint. This makes sense; by putting the implementation of these business rules in the model, we make sure that nothing else in the application can make our data invalid. The model acts as both a gatekeeper and a data store

The view is responsible for generating a user interface, normally based on data in the model. For example, an online store will have a list of products to be displayed on a catalog screen. This list will be accessible via the model, but it will be a view that accesses the list from the model and formats it for the end user. Although the view may present the user with various ways of inputting data, the view itself never handles incoming data. The view’s work is done once the data is displayed. There may well be many views that access the same model data, often for different purposes

Controllers orchestrate the application. Controllers receive events from the outside world (normally user input), interact with the model, and display an appropriate view to the user.


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