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Update the MVC explanation in the main README.rdoc file

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Jeff Cohen 2011-05-23 21:09:05 -05:00
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README.rdoc
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== Welcome to Rails
Rails is a web-application framework that includes everything needed to create
database-backed web applications according to the Model-View-Control pattern.
database-backed web applications according to the Model-View-Controller pattern.
This pattern splits the view (also called the presentation) into "dumb"
templates that are primarily responsible for inserting pre-built data in between
HTML tags. The model contains the "smart" domain objects (such as Account,
Product, Person, Post) that holds all the business logic and knows how to
persist themselves to a database. The controller handles the incoming requests
(such as Save New Account, Update Product, Show Post) by manipulating the model
and directing data to the view.
Understanding the MVC pattern is key to understanding Rails. MVC divides your application
into three layers, each with a specific responsibility.
In Rails, the model is handled by what's called an object-relational mapping
layer entitled Active Record. This layer allows you to present the data from
database rows as objects and embellish these data objects with business logic
methods. You can read more about Active Record in its
The View layer is composed of "templates" that are responsible for providing
appropriate representations of your application's resources. Templates
can come in a variety of formats, but most view templates are HTML with embedded Ruby
code (.erb files).
The Model layer represents your domain model (such as Account, Product, Person, Post)
and encapsulates the business logic that is specific to your application. In Rails,
database-backed model classes are derived from ActiveRecord::Base. ActiveRecord allows
you to present the data from database rows as objects and embellish these data objects
with business logic methods. Although most Rails models are backed by a database, models
can also be ordinary Ruby classes, or Ruby classes that implement a set of interfaces as
provided by the ActiveModel module. You can read more about Active Record in its
{README}[link:files/activerecord/README_rdoc.html].
The controller and view are handled by the Action Pack, which handles both
layers by its two parts: Action View and Action Controller. These two layers
are bundled in a single package due to their heavy interdependence. This is
unlike the relationship between the Active Record and Action Pack that is much
more separate. Each of these packages can be used independently outside of
Rails. You can read more about Action Pack in its
{README}[link:files/actionpack/README_rdoc.html].
The Controller layer handles incoming requests HTTP requests (such as Save New Account,
Update Product, Show Post). Controllers are responsible for providing a suitable response
back to the client (usually a web browser, but possibly an JSON or XML API client, etc.).
Controllers manipulate models and render the appropriate view templates to generate the HTTP response.
In Rails, the Controller and View layers are handled together by Action Pack.
These two layers are bundled in a single package due to their heavy interdependence.
This is unlike the relationship between the Active Record and Action Pack which are
independent. Each of these packages can be used independently outside of Rails. You
can read more about Action Pack in its {README}[link:files/actionpack/README_rdoc.html].
== Getting Started