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Diffstat (limited to 'activerecord/lib/active_record/acts/list.rb')
| -rw-r--r-- | activerecord/lib/active_record/acts/list.rb | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/acts/list.rb b/activerecord/lib/active_record/acts/list.rb new file mode 100644 index 0000000000..5d16f9a0c9 --- /dev/null +++ b/activerecord/lib/active_record/acts/list.rb @@ -0,0 +1,185 @@ +module ActiveRecord + # Mixins are a way of decorating existing Active Record models with additional behavior. If you for example + # want to keep a number of Documents in order, you can include Mixins::List, and all of the sudden be able to + # call <tt>document.move_to_bottom</tt>. + module Acts + # This mixin provides the capabilities for sorting and reordering a number of objects in list. + # The class that has this mixin included needs to have a "position" column defined as an integer on + # the mapped database table. Further more, you need to implement the <tt>scope_condition</tt> if you want + # to separate one list from another. + # + # Todo list example: + # + # class TodoList < ActiveRecord::Base + # has_many :todo_items, :order => "position" + # end + # + # class TodoItem < ActiveRecord::Base + # include ActiveRecord::Mixins::List + # belongs_to :todo_list + # + # private + # def scope_condition + # "todo_list_id = #{todo_list_id}" + # end + # end + # + # todo_list.first.move_to_bottom + # todo_list.last.move_higher + module List + def self.append_features(base) + super + base.extend(ClassMethods) + end + + module ClassMethods + def acts_as_list(options = {}) + configuration = { :column => "position", :scope => "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 !~ /_id$/ + + class_eval <<-EOV + include InstanceMethods + + def position_column + '#{configuration[:column]}' + end + + def scope_condition + "#{configuration[:scope].is_a?(Symbol) ? configuration[:scope].to_s + " = \#{" + configuration[:scope].to_s + "}" : configuration[:scope]}" + end + + before_destroy :remove_from_list + after_create :add_to_list_bottom + EOV + end + + module InstanceMethods + def move_lower + return unless lower_item + + self.class.transaction do + lower_item.decrement_position + increment_position + end + end + + def move_higher + return unless higher_item + + self.class.transaction do + higher_item.increment_position + decrement_position + end + end + + def move_to_bottom + self.class.transaction do + decrement_positions_on_lower_items + assume_bottom_position + end + end + + def move_to_top + self.class.transaction do + increment_positions_on_higher_items + assume_top_position + end + end + + + # Entering or existing the list + + def add_to_list_top + increment_positions_on_all_items + end + + def add_to_list_bottom + assume_bottom_position + end + + def remove_from_list + decrement_positions_on_lower_items + end + + + # Changing the position + + def increment_position + update_attribute position_column, self.send(position_column).to_i + 1 + end + + def decrement_position + update_attribute position_column, self.send(position_column).to_i - 1 + end + + + # Querying the position + + def first? + self.send(position_column) == 1 + end + + def last? + self.send(position_column) == bottom_position_in_list + end + + private + # Overwrite this method to define the scope of the list changes + def scope_condition() "1" end + + def higher_item + self.class.find_first( + "#{scope_condition} AND #{position_column} = #{(send(position_column).to_i - 1).to_s}" + ) + end + + def lower_item + self.class.find_first( + "#{scope_condition} AND #{position_column} = #{(send(position_column).to_i + 1).to_s}" + ) + end + + def bottom_position_in_list + item = bottom_item + item ? item.send(position_column) : 0 + end + + def bottom_item + self.class.find_first( + "#{scope_condition} ", + "#{position_column} DESC" + ) + end + + def assume_bottom_position + update_attribute position_column, bottom_position_in_list.to_i + 1 + end + + def assume_top_position + update_attribute position_column, 1 + end + + def decrement_positions_on_lower_items + self.class.update_all( + "#{position_column} = (#{position_column} - 1)", "#{scope_condition} AND #{position_column} > #{send(position_column).to_i}" + ) + end + + def increment_positions_on_higher_items + self.class.update_all( + "#{position_column} = (#{position_column} + 1)", "#{scope_condition} AND #{position_column} < #{send(position_column)}" + ) + end + + def increment_positions_on_all_items + self.class.update_all( + "#{position_column} = (#{position_column} + 1)", "#{scope_condition}" + ) + end + end + end + end + end +end
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