# File lib/active_record/associations.rb, line 694
      def belongs_to(association_id, options = {})
        if options.include?(:class_name) && !options.include?(:foreign_key)
          ::ActiveSupport::Deprecation.warn(
          "The inferred foreign_key name will change in Rails 2.0 to use the association name instead of its class name when they differ.  When using :class_name in belongs_to, use the :foreign_key option to explicitly set the key name to avoid problems in the transition.",
          caller)
        end
        
        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
      
          # deprecated api
          deprecated_has_association_method(reflection.name)
          deprecated_association_comparison_method(reflection.name, reflection.class_name)
        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?'"
          )          
        end
      end