gem install searchable_record

A brief usage example:

class Item < ActiveRecord::Base
  include SearchableRecord
end

rules = {
  :limit    => nil,                 # key as a flag; the value for the key is not used
  :offset   => nil,                 # key as a flag
  :sort     => { 'name' => 'items.name', 'created' => 'items.created_at' },
  :rsort    => nil,                 # rsort is allowed according to rules in :sort (key as a flag)
  :since    => 'items.created_at',  # cast parameter value as the default type
  :until    => 'items.created_at',  # cast parameter value as the default type
  :patterns => { :type => 'items.type', # match the pattern with the default operator and converter
                 :name => { :column    => 'items.name',
                            :converter => lambda { |val| "%#{val.gsub('_', '.')}%" } } }
                                    # match the pattern with the default operator
}

Item.find_queried(:all, params, rules)

See the gem website for details.