belongs_to (ActiveRecord::Associations::ClassMethods)

    # File lib/active_record/associations.rb, line 795
          def belongs_to(association_id, options = {})
            reflection = create_belongs_to_reflection(association_id, options)

            if reflection.options[:polymorphic]
              association_accessor_methods(reflection, BelongsToPolymorphicAssociation)

              module_eval do
                before_save "association = instance_variable_get(\"@\#{reflection.name}\")\nif association && association.target\nif association.new_record?\nassociation.save(true)\nend\n\nif association.updated?\nself[\"\#{reflection.primary_key_name}\"] = association.id\nself[\"\#{reflection.options[:foreign_type]}\"] = association.class.base_class.name.to_s\nend\nend\n"
              end
            else
              association_accessor_methods(reflection, BelongsToAssociation)
              association_constructor_method(:build,  reflection, BelongsToAssociation)
              association_constructor_method(:create, reflection, BelongsToAssociation)

              module_eval do
                before_save "association = instance_variable_get(\"@\#{reflection.name}\")\nif !association.nil?\nif association.new_record?\nassociation.save(true)\nend\n\nif association.updated?\nself[\"\#{reflection.primary_key_name}\"] = association.id\nend\nend\n"
              end
            end

            # Create the callbacks to update counter cache
            if options[:counter_cache]
              cache_column = options[:counter_cache] == true ?
                "#{self.to_s.underscore.pluralize}_count" :
                options[:counter_cache]

              module_eval(
                "after_create '#{reflection.name}.class.increment_counter(\"#{cache_column}\", #{reflection.primary_key_name})" +
                " unless #{reflection.name}.nil?'"
              )

              module_eval(
                "before_destroy '#{reflection.name}.class.decrement_counter(\"#{cache_column}\", #{reflection.primary_key_name})" +
                " unless #{reflection.name}.nil?'"
              )

              module_eval(
                "#{reflection.class_name}.send(:attr_readonly,\"#{cache_column}\".intern) if defined?(#{reflection.class_name}) && #{reflection.class_name}.respond_to?(:attr_readonly)"
              )
            end
          end