Module: ActiveRecord::Acts::List::ClassMethods

Defined in:
lib/acts_as_list/active_record/acts/list.rb

Overview

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

Instance Method Summary (collapse)

Instance Method Details

- (Object) 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 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 like an array in its indexing.

  • add_new_at - specifies whether objects get added to the :top or :bottom of the list. (default: bottom)



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# File 'lib/acts_as_list/active_record/acts/list.rb', line 36

def acts_as_list(options = {})
  configuration = { :column => "position", :scope => "1 = 1", :top_of_list => 1, :add_new_at => :bottom}
  configuration.update(options) if options.is_a?(Hash)

  configuration[:scope] = "#{configuration[:scope]}_id".intern if configuration[:scope].is_a?(Symbol) && configuration[:scope].to_s !~ /_id$/

  if configuration[:scope].is_a?(Symbol)
    scope_condition_method = %(
      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 = %(
      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 <<-EOV
    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 :reload_position
    after_destroy :decrement_positions_on_lower_items
    before_create :add_to_list_#{configuration[:add_new_at]}
    after_update :update_positions
  EOV
end