Module: ActiveRecord::AttributeMethods::Read

'id'.freeze

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