MVC
(Model-view-controller)
OverView
- MVC (Model-View-Controller)
- Software Architectural pattern for implementing user interfaces
- Divides the work of an application into three separate but closely cooperative subsystems.
- This seperation helps you manage complex applications
- Divided into 3 components
- Model: responsible for maintaining data
-
View: responsible for displaying the data to the user
- Controller: controls the interactions between the M and V
Overview
Model
-
Retrieves data from a database
- Stores data to a database
- Responds to instructions from the controller to update itself
-
Possibly updates itself from view as well ( But not recommended)
- The bulk of your application’s business logic will be concentrated in the models
View
- Views represent the user interface of your application
- Views are often HTML files with embedded code which perform tasks related solely to the presentation of the data
- Handles the job of providing data to the web browser or other tool that is used to make requests from your application
Controller
- The controller is the decision maker and the glue between the model and the view
- Responsible for
- processing the incoming requests from the web browser
- interrogating the models for data
- passing that data on to the views for presentation
RUBY ON RAILS
Introduction
- Creator of ROR: David Heinemeier Hansson(DHH)
- Open-source
- Web application development framework written in the Ruby language
- Full-stack framework for developing web applications according to the MVC pattern
- Productivity: Write less code and get it done
- Where development is fun
ROR Philosophy
- Don't Repeat Yourself(DRY):
- DRY : "Every piece of knowledge must have a single and unambiguous representation within a system."
- By not writing the same information over and over again, our code is more maintainable, extensible, and less buggy.
- Convention Over Configuration:
- Rails has opinions about the best way to do many things in a web application, and defaults to this set of conventions, rather than require that you specify every minute details through endless configuration files.
Architecture
- Rails applications are implemented using the Model-View-Controller (MVC) architectural pattern
- Model – ActiveRecord
- View – ActionView
- Controller - ActionController
Directory Layout
- Rails applications have a common directory structure
/app - the MVC core
/controllers
/helpers - provides extra functionality for views
/models
/views/nameofcontroller - templates for controller actions
/assets
/mailers – mailer classes to send mails
Rails Environments
- Rails runs in different modes, depending on the parameters given to the server on startup.
- Each mode defaults to it’s own database schema
- Development (verbose logging and error messages)
- Test
- Production
Creating Rails Application
- rails new app_name –database=mysql
- cd app_name
- rake db:create
- rails s
Models
-
ORM (Object Relational Mapping) : ActiveRecord
- Generator
- Rails g model Product name:string quantity:integer
- Callbacks
- Validations
- Finders
- Querying
- Asscociations
VIEW
- erb , haml
- partials
- View helpers
- Form helpers
- Route helpers
CONTROLLER
- Generater
- rails g controller books
- Filters
- before_filter
- after_filter
- arround_filter
- Render Views
- respond_to
ROUtes
- One can check all routes using "rake routes"
- Mapping urls to controller and actions
get '/patients/:id', to: 'patients#show', as: 'patient'- Resources
resources :photos- Namespace
namespace :admin do resources :posts, :comments end
ROUTES
- Nesting routes
resources :magazines do resources :ads end- Limiting REST routes (7 default routes index, new, create, edit, update, destroy, show)
resources :comments, only: [:index, :new, :create]
MVC in Detail
Migration
- Create table, change column, add and remove columns etc
- Generator
- rails g migration add_column_name_to_table_name column_name:datatype
- Running migration
- rake db:migrate
- rake db:migrate:down VERSION=timestamp_version
- rake db:migrate:up VERSION=timestamp_version
- rake db:migrate:status
- rake db:rollback
References
- http://www.railstutorial.org/book/beginning
- http://en.wikipedia.org/wiki/Model-view-controller
-
http://guides.rubyonrails.org/