require 'active_support/core_ext/module/method_transplanting' module ActiveRecord module AttributeMethods module Read ReaderMethodCache = Class.new(AttributeMethodCache) { private # We want to generate the methods via module_eval rather than # define_method, because define_method is slower on dispatch. # Evaluating many similar methods may use more memory as the instruction # sequences are duplicated and cached (in MRI). define_method may # be slower on dispatch, but if you're careful about the closure # created, then define_method will consume much less memory. # # But sometimes the database might return columns with # characters that are not allowed in normal method names (like # 'my_column(omg)'. So to work around this we first define with # the __temp__ identifier, and then use alias method to rename # it to what we want. # # We are also defining a constant to hold the frozen string of # the attribute name. Using a constant means that we do not have # to allocate an object on each call to the attribute method. # Making it frozen means that it doesn't get duped when used to # key the @attributes in read_attribute. def method_body(method_name, const_name) <<-EOMETHOD def #{method_name} name = ::ActiveRecord::AttributeMethods::AttrNames::ATTR_#{const_name} read_attribute(name) { |n| missing_attribute(n, caller) } end EOMETHOD end }.new extend ActiveSupport::Concern module ClassMethods [:cache_attributes, :cached_attributes, :cache_attribute?].each do |method_name| define_method method_name do |*| cached_attributes_deprecation_warning(method_name) true end end protected def cached_attributes_deprecation_warning(method_name) ActiveSupport::Deprecation.warn "Calling `#{method_name}` is no longer necessary. All attributes are cached." end if Module.methods_transplantable? def define_method_attribute(name) method = ReaderMethodCache[name] generated_attribute_methods.module_eval { define_method name, method } end else def define_method_attribute(name) safe_name = name.unpack('h*').first temp_method = "__temp__#{safe_name}" ActiveRecord::AttributeMethods::AttrNames.set_name_cache safe_name, name generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__ + 1 def #{temp_method} name = ::ActiveRecord::AttributeMethods::AttrNames::ATTR_#{safe_name} read_attribute(name) { |n| missing_attribute(n, caller) } end STR generated_attribute_methods.module_eval do alias_method name, temp_method undef_method temp_method end end end end # Returns the value of the attribute identified by attr_name after # it has been typecast (for example, "2004-12-12" in a date column is cast # to a date object, like Date.new(2004, 12, 12)). def read_attribute(attr_name, &block) name = attr_name.to_s name = self.class.primary_key if name == 'id' @attributes.fetch_value(name, &block) end private def attribute(attribute_name) read_attribute(attribute_name) end end end end