create_check_with_enumeration.rb

# For example, in a migration
#
#  create_check_with_enumeration :foobars, :column => :category, :with => FoobarsCategory
#
# will create a check constraint in the table "foobars", so the column "category" will only accept one 
# of the values declared in the FoobarsCategory enumeration
#
module ActiveRecord
  module ConnectionAdapters
    class PostgreSQLAdapter < AbstractAdapter
      def create_check_with_enumeration(table, options)
        options.assert_valid_keys :column, :with
        [:column, :with].each { |opt| raise "You must pass an #{opt} option" if options[opt].blank? }
        list = options[:with].list.map { |v| v.is_a?(String) ? "'#{v}'" : v }.join(", ")
        execute %Q{alter table #{table} add constraint #{table}_#{options[:column]}_check check (#{options[:column]} in (#{list}))}
      end
    end
  end
end