CSC/ECE 517 Fall 2011/ch4 4e ar

Lecture 10

Model, View and Controller

Model

Definition: The model represents all the data in the application.

A model is typically mapped to a table in the database. It maintains the state of an application and responds to changes to alter it. The model provides the developer with a consistent interface to handle and manipulate the data in an application. It hides a object-relation-mapping underneath, allowing the application to be portable to various database management systems. The model also validates the data before storing it. The code for a model can be found in the apps/models directory of a rails project.

View

Definition: A view renders the model in a form suitable for the user to comprehend.

A view queries the model to obtain data and generates an interface to display it. Typically, the controller instructs a view to render itself. However, in some cases, the view is automatically notified by the model of changes in state. The code for the views can be found in the app/views directory of a rails project.

Controller

Definition: A controller accepts input from the user and instructs the rest of the framework to respond to it.

Typically, the user input is modeled as an event and the controller converts it to a user action, understandable by the model. Based on the input, it also decides which views to render. The controller is also responsible for a number of auxiliary services like session management, caching and helper modules. Code for a controller can be found in the app/controllers/ directory of a rails project.