Randika on Rails

I keep forgetting all those fancy ruby on rails commands and the important code snippets always. I better keep them documented some where I can find easily. So I’m going to write down as much as code snippets, command lines, tips tricks where I need. Anyway this looks messy as I update this page time to time, hope you also can contribute for the list. I hope this will help someone else too.

How to add/remove new columns to table (models) ?
you can specify columns you want to add/remove in your migration by passing attribute:type pairs to the migration generator command line. here is an example to add the mobile number to existing user model.

[randika@localhost MyApp]$ script/generate migration AddMobileToUser mobile:string

and run the rake db:migrate command. This will create the migration schema for you as:

class AddMobileToUser < ActiveRecord::Migration
  def self.up
    add_column :users, :mobile, :string
  end
 
  def self.down
    remove_column :users, :mobile
  end
end

Similarly when you need to remove a column try using below command, followed by the the rake db:migrate

[randika@localhost MyApp]$ script/generate migration RemoveMobileFromUser mobile:string

How to create dynamic drop down menu from a another model

<%= f.select :country_id, Country.all.collect {|country| [ country.name, country.id ] } %>

this will output:

<select id="country_country_id" name="country[country_id]">
<option value="1">Country A</option>
<option value="2">Country B</option>
<option value="3">Country C</option>
</select>

How to find the configuration settings, versions of the development environment

• To determine the version of Rails that you are running, you can issue rails -v at a command prompt.

$rails -v

• To determine the Rails installation path type which rails at a command prompt. (only on linux)

$which rails

• To determine the list of gems installed type gem list

$gem list

How to print the month name from a month number


Putting this code in a view, will print “December” as the output.

<%= Date::MONTHNAMES[12] %>

How to assign a css class to link_to method in Ruby on Rails

How to install/start mongrel http server

$ sudo gem install mongrel
$ cd yourrailsapp
$ mongrel_rails start -d

How to stop mongrel http server

$ mongrel_rails stop