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

#acts_as_list(options = {}) ⇒ Object

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)

    `nil` will result in new items not being added to the list on create



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# File 'lib/acts_as_list/active_record/acts/list.rb', line 37

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)

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

  caller_class = self

  class_eval do
    define_singleton_method :acts_as_list_top do
      configuration[:top_of_list].to_i
    end

    define_method :acts_as_list_top do
      configuration[:top_of_list].to_i
    end

    define_method :acts_as_list_class do
      caller_class
    end

    define_method :position_column do
      configuration[:column]
    end

    define_method :scope_name do
      configuration[:scope]
    end

    define_method :add_new_at do
      configuration[:add_new_at]
    end

    define_method :"#{configuration[:column]}=" do |position|
      write_attribute(configuration[:column], position)
      @position_changed = true
    end

    if configuration[:scope].is_a?(Symbol)
      define_method :scope_condition do
        { configuration[:scope] => send(:"#{configuration[:scope]}") }
      end

      define_method :scope_changed? do
        changed.include?(scope_name.to_s)
      end
    elsif configuration[:scope].is_a?(Array)
      define_method :scope_condition do
        configuration[:scope].inject({}) do |hash, column|
          hash.merge!({ column.to_sym => read_attribute(column.to_sym) })
        end
      end

      define_method :scope_changed? do
        (scope_condition.keys & changed.map(&:to_sym)).any?
      end
    else
      define_method :scope_condition do
        eval "%{#{configuration[:scope]}}"
      end

      define_method :scope_changed? do
        false
      end
    end

    # only add to attr_accessible
    # if the class has some mass_assignment_protection
    if defined?(accessible_attributes) and !accessible_attributes.blank?
      attr_accessible :"#{configuration[:column]}"
    end

    define_singleton_method :quoted_position_column do
      @_quoted_position_column ||= connection.quote_column_name(configuration[:column])
    end

    define_singleton_method :quoted_position_column_with_table_name do
      @_quoted_position_column_with_table_name ||= "#{caller_class.quoted_table_name}.#{quoted_position_column}"
    end

    scope :in_list, lambda { where("#{quoted_position_column_with_table_name} IS NOT NULL") }

    define_singleton_method :decrement_all do
      update_all_with_touch "#{quoted_position_column} = (#{quoted_position_column_with_table_name} - 1)"
    end

    define_singleton_method :increment_all do
      update_all_with_touch "#{quoted_position_column} = (#{quoted_position_column_with_table_name} + 1)"
    end

    define_singleton_method :update_all_with_touch do |updates|
      record = new
      attrs = record.send(:timestamp_attributes_for_update_in_model)
      now = record.send(:current_time_from_proper_timezone)

      query = attrs.map { |attr| "#{connection.quote_column_name(attr)} = :now" }
      query.push updates
      query = query.join(", ")

      update_all([query, now: now])
    end
  end

  attr_reader :position_changed

  before_validation :check_top_position

  before_destroy :lock!
  after_destroy :decrement_positions_on_lower_items

  before_update :check_scope
  after_update :update_positions

  after_commit :clear_scope_changed

  if configuration[:add_new_at].present?
    before_create "add_to_list_#{configuration[:add_new_at]}".to_sym
  end

  include ::ActiveRecord::Acts::List::InstanceMethods
end