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
Public Instance 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‘
    # File vendor/rails/activerecord/lib/active_record/acts/list.rb, line 33
33:         def acts_as_list(options = {})
34:           configuration = { :column => "position", :scope => "1 = 1" }
35:           configuration.update(options) if options.is_a?(Hash)
36: 
37:           configuration[:scope] = "#{configuration[:scope]}_id".intern if configuration[:scope].is_a?(Symbol) && configuration[:scope].to_s !~ /_id$/
38:           
39:           if configuration[:scope].is_a?(Symbol)
40:             scope_condition_method = %(
41:               def scope_condition
42:                 if #{configuration[:scope].to_s}.nil?
43:                   "#{configuration[:scope].to_s} IS NULL"
44:                 else
45:                   "#{configuration[:scope].to_s} = \#{#{configuration[:scope].to_s}}"
46:                 end
47:               end
48:             )
49:           else
50:             scope_condition_method = "def scope_condition() \"#{configuration[:scope]}\" end"
51:           end
52:           
53:           class_eval "include ActiveRecord::Acts::List::InstanceMethods\n\ndef acts_as_list_class\n::\#{self.name}\nend\n\ndef position_column\n'\#{configuration[:column]}'\nend\n\n\#{scope_condition_method}\n\nafter_destroy  :remove_from_list\nbefore_create  :add_to_list_bottom\n"
54:         end