module ActiveRecord::Acts::List::ClassMethods

This acts_as extension 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

Public Instance Methods

acts_as_list(options = {}) click to toggle source

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 it hasn't already been added) 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'

  • top_of_list - defines the integer used for the top of the list. Defaults to 1. Use 0 to make the collection act more line an array in it's indexing.

# File lib/acts_as_list/active_record/acts/list.rb, line 35
        def acts_as_list(options = {})
          configuration = { :column => "position", :scope => "1 = 1", :top_of_list => 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
                self.class.send(:sanitize_sql_hash_for_conditions, { :#{configuration[:scope].to_s} => send(:#{configuration[:scope].to_s}) })
              end
            )
          elsif configuration[:scope].is_a?(Array)
            scope_condition_method = %Q(
              def scope_condition
                attrs = %w(#{configuration[:scope].join(" ")}).inject({}) do |memo,column| 
                  memo[column.intern] = send(column.intern); memo
                end
                self.class.send(:sanitize_sql_hash_for_conditions, attrs)
              end
            )
          else
            scope_condition_method = "def scope_condition() \"#{configuration[:scope]}\" end"
          end

          class_eval "            include ActiveRecord::Acts::List::InstanceMethods

            def acts_as_list_top
              #{configuration[:top_of_list]}.to_i
            end

            def acts_as_list_class
              ::#{self.name}
            end

            def position_column
              '#{configuration[:column]}'
            end

            #{scope_condition_method}

            before_destroy :decrement_positions_on_lower_items
            before_create  :add_to_list_bottom
"
        end