ReaderMethodCache = { 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_cache 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
ATTRIBUTE_TYPES_CACHED_BY_DEFAULT = [:datetime, :timestamp, :time, :date]
Instance Public methods

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, 12, 12)).

# File activerecord/lib/active_record/attribute_methods/read.rb, line 107
def read_attribute(attr_name)
  # If it's cached, just return it
  # We use #[] first as a perf optimization for non-nil values. See
  name = attr_name.to_s
  @attributes_cache[name] || @attributes_cache.fetch(name) {
    column = @column_types_override[name] if @column_types_override
    column ||= @column_types[name]

    return @attributes.fetch(name) {
      if name == 'id' && self.class.primary_key != name
    } unless column

    value = @attributes.fetch(name) {
      return block_given? ? yield(name) : nil

    if self.class.cache_attribute?(name)
      @attributes_cache[name] = column.type_cast(value)
      column.type_cast value