I would like to add a selection list country field in a view but first i need to get the a country hash from the Country model.

In Rails ActiveRecord, the Model.find() method returns an array
of objects from the database, so what i need to do is converting the returned array into a hash object and i have already talked about this in the previous post
Ruby – Convert Array into Hash

But the array which i get from the ActiveRecord is not the same as the above example. Anyway, the following did work for me to get a country hash.
app/model/country.rb

class Country < ActiveRecord::Base

  def self.hashify
    @country_array = Country.find(:all, :select => 'name, code').to_a
    @country_hash = @country_array.inject({}) do |result, element|
      result[element[:name]] = element[:code]
      result
    end
  end
end

Now you can get the hash object by

@countries = Country.hashify

This the the resulted country hash.

{
  "Afghanistan"=>"AF",
  "Aland Islands"=>"AX",
  "Albania"=>"AL",
  ...
  "Zambia"=>"ZM",
  "Zimbabwe"=>"ZW"
}

Done =)

Update 2012-03-08: A simpler way to get the hash object suggested by Filipe as follow.

@country_hash = Hash[*Country.all.collect {|it| [it.name, it.code]}.flatten]

Thanks Filipe.