Ruby on Rails: Getting Started Part I

Most people are fairly familiar with the basic idea of a database driven website. More specifically, they understand that data is stored in the database and somehow makes it into the web page the browser loads.

Ruby on Rails provides a framework that makes the transition of information from a database to a webpage extremely simple. To begin, we’ll assume that you have Ruby and Rails installed on your machine. From there, we’ll work our way up from the database to the core of the application and back out into the webpage that presents the data.

First, create your new application

In this example, we’ll be creating a simple blog.

rails simple_blog

Second, set up your database

In this case, steps 2 and three blur a little. This is because Ruby on Rails provides scripts called generators, which create certain files with certain functionality built in. We’ll explain that part in a minute.

First, we need to tell your new blog where the database is that it will be using. To do that, open the file at config/database.yml in your favorite text editor. In this tutorial, we’ll be using vim.

cd simple_blog
vim config/database.yml

You should see a file that looks something like this:

# SQLite version 3.x
#   gem install sqlite3-ruby (not necessary on OS X Leopard)
development:
  adapter: sqlite3
  database: db/development.sqlite3
  pool: 5
  timeout: 5000

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: sqlite3
  database: db/test.sqlite3
  pool: 5
  timeout: 5000

production:
  adapter: sqlite3
  database: db/production.sqlite3
  pool: 5
  timeout: 5000

We are going to change our database configuration to use mysql.

development:
  adapter: mysql
  database: blog_development
  username: root
  timeout: 5000

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: mysql
  database: blog_test
  username: root
  timeout: 5000

production:
  adapter: mysql
  database: blog_production
  username: root
  timeout: 5000

In this example, the root password is blank. You can add a ‘password:’ field to each database that needs a password where necessary. The ‘pool:’ field we left out will cause Ruby on Rails to connect across a pool of connections. The default in this case is 5 connection per pool.

Now that we’ve told Ruby on Rails where to go for its data, it’s time to begin defining that data. The types of data we’ll be dealing with in these cases are: users, posts, and categories. We can define these data types by using the generator scripts:

script/generate model user username:string password:string full_name:string
script/generate model post title:string content:text
script/generate model category name:string

You’ll see the generator creates several files. The one we’re going to talk about for step 2 is the database migration. The database migrations are scripts that modify your database. Let’s open the database migration for our user data.

vim db/migrate/*_create_users.rb

class CreateUsers < ActiveRecord::Migration
  def self.up
    create_table :users do |t|
      t.string :username
      t.string :password
      t.string :full_name

      t.timestamps
    end
  end

  def self.down
    drop_table :users
  end
end

The migration above does exactly what it looks like it does. It creates a table with three string columns and some timestamps. It also creates a column on each table called ‘id’ that is the unique id for each row in the table.

Now that we have the database migrations ready to go, let’s run them and get our database ready to start accepting data.

rake db:migrate

Now that you’re set up and have run your migrations, open up your MySQL browsing software or command line and check out your database structure and we’ll come back around to Models accessing your data in Part II.