# 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 https://gist.github.com/jonleighton/3552829.
  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
        read_attribute(self.class.primary_key)
      end
    } 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)
    else
      column.type_cast value
    end
  }
end