Rails Basics : What is a Model ?

What is a Model ?

The Model is the 'M' in the MVC (Model/Views/Controller) concept integral to a Rails application.

Models should :-

• Constitute most of your application codes. 
• Provide  a persistent storage mechanism to your database
• Define all business logic
  

In a nutshell, Models should be the brains that operate on your application's database, determine and change the state of other objects and co-ordinate the overall business logic of your applications.

Conventions for Models

Model classes in Rails are all inherited from the ActiveRecord base class ActiveRecord::Base and map one-to-one to a table in your database.

Residing in the app/models directory, Models should following the following convention :-

• Only one class per file
• Class name should be singular and camel-cased eg.Customer or BillNo
• Corresponding table name should be lowercased, plural and underscored eg. customers or bill_nos
• Corresponding table must have an auto-incrementing integer field called id
• Column names shoudl also be lowercased
• Model filename should be lowercased and underscored version of the class name eg. customer.rb or bill_no.rb
  

To represent the relationship between tables and columns in your application, ActiveRecord provides the following set of methods called associations :-

• has_many represents a zero-to-many relationship between the Parent & Child Class
  
• belongs_to is the reciprocal child method to parent has_many method
  
• has_one  is like a belongs_to and represents a one-to-one relationship in your database
  

More to come...