def belongs_to(association_id, options = {})
options.assert_valid_keys(:class_name, :foreign_key, :remote, :conditions, :order, :include, :dependent, :counter_cache, :extend)
association_name, association_class_name, class_primary_key_name =
associate_identification(association_id, options[:class_name], options[:foreign_key], false)
require_association_class(association_class_name)
association_class_primary_key_name = options[:foreign_key] || association_class_name.foreign_key
association_accessor_methods(association_name, association_class_name, association_class_primary_key_name, options, BelongsToAssociation)
association_constructor_method(:build, association_name, association_class_name, association_class_primary_key_name, options, BelongsToAssociation)
association_constructor_method(:create, association_name, association_class_name, association_class_primary_key_name, options, BelongsToAssociation)
module_eval do
before_save "association = instance_variable_get(\"@\#{association_name}\")\nif not association.nil?\nif association.new_record?\nassociation.save(true)\nassociation.send(:construct_sql)\nend\nself[\"\#{association_class_primary_key_name}\"] = association.id if association.updated?\nend\n"
end
if options[:counter_cache]
module_eval(
"after_create '#{association_class_name}.increment_counter(\"#{self.to_s.underscore.pluralize + "_count"}\", #{association_class_primary_key_name})" +
" unless #{association_name}.nil?'"
)
module_eval(
"before_destroy '#{association_class_name}.decrement_counter(\"#{self.to_s.underscore.pluralize + "_count"}\", #{association_class_primary_key_name})" +
" unless #{association_name}.nil?'"
)
end
deprecated_has_association_method(association_name)
deprecated_association_comparison_method(association_name, association_class_name)
end