Ruby On Rails for Beginners

Rails is a web-application framework that includes everything needed to create database-backed web applications according to the Model-View-Control pattern.
Rails is a collection ruby script. It’s better to have basic idea of ruby language before entering into Rails.
Rails has the following things

1. An Application framework /Action Pack that will help us to
generate data-driven, interactive pages.
2. Rails comes with one build in WebServer -We can run the web
application
3. Database-Rails creates application that are configured to
work with an integrated SQLite3 database
4. Active Record-Rails provides for object-relational mapping
library. This makes the database like a collection of Ruby objects.
5. Rails also provide the collection of tool scripts that helps
to manage the application.

Principle in Rails: Don’t Repeat Yourself
[If we tell Rails something once,its not required to say it again]

Install Ruby on Rails or RoR version2.1 & SQLite3 for database
http://www.rubyonrails.org/down

Getting started with Application

I - Steps to create a new application in Rails
1. At a Command Prompt –type >rails Application name
  Ex: C:\ >rails MyApp

A New Folder names MyApp will be created with basic structure of the
application.
The basic Structure has the following folders &files
App,Config,Db,Doc,Lib,Log,Public,Script, test, tmp, vendor ,Rake files & readme
file

2.In that command prompt change into MyApp folder C:\MyApp>.
Type ruby script/server –To run the web server.

  Ex: C:\MyApp>ruby script/server

3.Check this link http://localhost:3000/ to
confirm whether the webserver running Rails starts its webserver on port 3000 by default.

II -Start developing the Application

CRUD operation
CRUD operation/ Scaffolding –Basic operation of an application
Create,Read,Update & Delete.
Type scaffold command _Will generate the code for doing CRUD
operation in a database and also in the presentation layer .

 Ex: C:\MyApp\>ruby script/generate scaffold employee employee_name:string
address:text

Creates employee.rb file in models & create_employees.rb
file in Db -migrate

[Note: We have to give the db name in singular form like
Employee,Shop..etc., and the table name will be in plural like
employees,Shops..etc.,]

To create the Tables in the database

We have to run the migration script using another rails tool called Rake.This
migration ruby script is generated by the scaffolding.

Type rake db:migrate at the command prompt –Which runs the
migration code& creates the table.[Db files are location the db folder]

  Ex:C:\MyApp\>rake db:migrate

 Run the employees.rb file in Db –migrate & create the table.

Go for link http://localhost:3000/employees In a couple of minutes we
can enter few records & perform the CRUD operations.


In app folder we will have Model, Controller & View folders .

To changes the display of the page

We can make the changes in the labels by changing the four .html.erb files in
the views folder.

To append a column after creating the Table.
Rails understand the migration Add..To..=>Add particular column
to a particular table.
Ex:If we want to include Phone Number column in employees table.

  C:\MyApp\>ruby script/generate migration
AddPhoneToEmployees phone:string
Rails write the migration code.

After this command we have to give Rake db:migrate to make the
reflection of new column in the table.
Go for link http://localhost:3000/employees to conifrm the addition of
one more column in the table.
We can check the changes whenever we update the code.No need for publish & deploy
operations.

Without Scaffolding
We are in some time need of writing the code by our self for some application.Instead of having the same basic CRUD functions.We might be in need of genearating our own models & controllers

Command to create own model
 ruby script/generate model table name in singular form column name:type

>  rake db:migrate

This command will create magic columns
 Id – Generated Primary Key.
 Created_at and updated_at – record when data is entered or updated

Command to create own controller
> ruby script/generate controller
A Controller file will be created in the controller folder.

III- Routes
Route tells Tails where the web pages are located.
Routes are defined in a ruby program in config/routes.rb

By default this two line swill be the routes.rb

  map.connect ':controller/:action/:id'
  map.connect ':controller/:action/:id.:format'

We can specify our own routes.
 Ex:map.connect '/employees/:id',:controller=>'employees',:action=>'show'

The controller by using the finder method in the model sends the employees to the view

employees_controller.rb file

  Class employeesController < ApplicationController
     Def show
        @employee=Employee.find(params[:id])
     end
  end

Rails Layout
Super-template exists in Rails is called Layout. one Single
template that will control how a group of other templates will look.
We have to place the html.erb file in the app/views/layouts.

To Add the style-sheet in the
Style sheet, images & javascripts will resides in the public folder.Which has all the static files.
Include the following code in the head tag of the html template.

   <%=stylesheet_link_tag 'style sheet name(css)'>

Redirect
A redirect tells the browser to go to a different URL for output.
  redirect_to "/---/# {---}"
# -symbol and {} inserts the value of the variable into a string.
Ex: While creating a new sample .We have to redirect to the currently
created sample.

     def create
          @sample = Sample.new(params[:sample])
          @sample.save
          redirect_to "/samples/#{@sample.id}"
     end

Restricting access to a function
Rails will use special kind of web security called HTTP Authenticating .This type of security will pops up a dialog box and asks for a username and password when someone tries to enter a secure area of a website.
In the controller we have to specify the following code to make the filtration before doing security applied functions.

before_filter :function name to be called before executing particular function,;only=>[:security applied operation name]

function name to be called before particular operations

  def functionname
    authenticate_or_request_with_http_basic("The name of the secured area of the website-domain") do |username,password| 
    username == "username "&& password =="password"
     end
  end

Ex:

 class SampleController <ApplicationController   before_filter   check_logged_in,:only=>[:edit]
  def check_logged_in
    authenticate_or_request_with_http_basic("Samples") do |username,password| 
   username == 'admin' && password =="XY2HYS8"
  end
  end  
 end