This act provides the capabilities for sorting and reordering a number of objects in a list. The class that has this specified needs to have a “position” column defined as an integer on the mapped database table.

Todo list example:

class TodoList < ActiveRecord::Base
  has_many :todo_items, :order => "position"
end

class TodoItem < ActiveRecord::Base
  belongs_to :todo_list
  acts_as_list :scope => :todo_list
end

todo_list.first.move_to_bottom
todo_list.last.move_higher
Methods
A
Instance Public methods
acts_as_list(options = {})

Configuration options are:

  • column - specifies the column name to use for keeping the position integer (default: position)

  • scope - restricts what is to be considered a list. Given a symbol, it'll attach "_id" (if that hasn't been already) and use that as the foreign key restriction. It's also possible to give it an entire string that is interpolated if you need a tighter scope than just a foreign key. Example: acts_as_list :scope => 'todo_list_id = #{todo_list_id} AND completed = 0'

Source: show 

# File rails/activerecord/lib/active_record/acts/list.rb, line 33
        def acts_as_list(options = {})
          configuration = { :column => "position", :scope => "1 = 1" }
          configuration.update(options) if options.is_a?(Hash)

          configuration[:scope] = "#{configuration[:scope]}_id".intern if configuration[:scope].is_a?(Symbol) && configuration[:scope].to_s !~ %r_id$/
          
          if configuration[:scope].is_a?(Symbol)
            scope_condition_method = %Q(
              def scope_condition
                if #{configuration[:scope].to_s}.nil?
                  "#{configuration[:scope].to_s} IS NULL"
                else
                  "#{configuration[:scope].to_s} = \#{#{configuration[:scope].to_s}}"
                end
              end
            )
          else
            scope_condition_method = "def scope_condition() \"#{configuration[:scope]}\" end"
          end
          
          class_eval "            include ActiveRecord::Acts::List::InstanceMethods

            def acts_as_list_class
              ::#{self.name}
            end
            
            def position_column
              '#{configuration[:column]}'
            end
            
            #{scope_condition_method}
            
            before_destroy :remove_from_list
            before_create  :add_to_list_bottom
"
        end