Rails3

Developing for Rails3.

Create a new application

Test your installation by making a test application

rails new tetsApp
cd testApp
rails server

Now check the http://localhost:3000 in your browser.

Nonstop first app

This example is adapted from here

rails new blog
cd blog
bundle install

gedit config/database.yml
rake db:create

rails generate controller home index
gedit app/views/home/index.html.erb

Enter the new web page content:

<h1>Hi there!</h1>

Set up the new root page

rm public/index.html
gedit config/routes.rb

Edit routes, like this

...
root :to => "home#index"
...

Test your server at http://localhost:3000

rails server

Create scaffolding

rails generate scaffold Post name:string title:string content:text
rake db:migrate

Database

Using Mysql

database.yml file

development:

 adapter: mysql2
 encoding: utf8
 database: blog_development
 pool: 5
 username: root<change this>
 password: <change this>
 socket: /tmp/mysql.sock

Using Postgres

Make sure you have pg gem installed (not the old "postgres" gem)

gem install pg

Making a new application

rails -d postgresql my_rails_app

database.yml file

  development:
   adapter: postgresql
   host: localhost
   port: 5432
   username: your_db_username
   password: your_db_password
   database: your_rails_project_development
   schema_search_path: public
   encoding: utf8
   template: template0

Reset database

Reset database contents

rake db:reset
rake db:migrate

or

rake db:reset db:migrate

Recreate database structure

rake db:drop
rake db:create
rake db:migrate

or

rake db:drop db:create db:migrate

Cardinality and associations

Active Record associations can be used to describe one-to-one, one-to-many and many-to-many relationships between models. Each model uses an association to describe its role in the relation.

The belongs_to association is always used in the model that has the foreign key.

one-to-one

class Employee < ActiveRecord::Base
  has_one :office
end
class Office < ActiveRecord::Base
  belongs_to :employee    # foreign key - employee_id
end

many-to-one

class Manager < ActiveRecord::Base
  has_many :employees
end
class Employee < ActiveRecord::Base
  belongs_to :manager     # foreign key - manager_id
end

many-to-many

Method 1. With an intermediate table (Assignment)

class Assignment < ActiveRecord::Base
  belongs_to :programmer  # foreign key - programmer_id
  belongs_to :project     # foreign key - project_id
end
class Programmer < ActiveRecord::Base
  has_many :assignments
  has_many :projects, :through => :assignments
end
class Project < ActiveRecord::Base
  has_many :assignments
  has_many :programmers, :through => :assignments
end

Method 2. With an intermediate table that has neither model nor primary key

class Programmer < ActiveRecord::Base
  has_and_belongs_to_many :projects       # foreign keys in the join table
end
class Project < ActiveRecord::Base
  has_and_belongs_to_many :programmers    # foreign keys in the join table
end

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More here

Database field types

Rails Migration Symbol	MySQL Data Type
:binary	blob
:boolean	tinyint(1)
:date	date
:datetime	datetime
:decimal	decimal
:float	float
:integer	int(11)
:string	varchar(255)
:text	text
:time	time
:timestamp	datetime

UTF-8

If you need UTF-8 encoding for your text in program files, add this magic comment to your file:

# encoding: utf-8

If you need UTF-8 in your (mysql) database(s), add "encoding: utf8" in the config/database.yml

 adapter: mysql
 ...
 encoding: utf8

More info

• RailsCasts tutorials

• About using postgres

See also RVM