Methods
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Instance Public methods
cache_attribute?(attr_name)

Returns true if the provided attribute is being cached.

Source: show | on GitHub 

# File activerecord/lib/active_record/attribute_methods/read.rb, line 28
def cache_attribute?(attr_name)
  cached_attributes.include?(attr_name)
end
cache_attributes(*attribute_names)

cache_attributes allows you to declare which converted attribute values should be cached. Usually caching only pays off for attributes with expensive conversion methods, like time related columns (e.g. created_at, updated_at).

Source: show | on GitHub 

# File activerecord/lib/active_record/attribute_methods/read.rb, line 17
def cache_attributes(*attribute_names)
  cached_attributes.merge attribute_names.map { |attr| attr.to_s }
end
cached_attributes()

Returns the attributes which are cached. By default time related columns with datatype :datetime, :timestamp, :time, :date are cached.

Source: show | on GitHub 

# File activerecord/lib/active_record/attribute_methods/read.rb, line 23
def cached_attributes
  @cached_attributes ||= columns.select { |c| cacheable_column?(c) }.map { |col| col.name }.to_set
end
undefine_attribute_methods()

Source: show | on GitHub 

# File activerecord/lib/active_record/attribute_methods/read.rb, line 32
def undefine_attribute_methods
  generated_external_attribute_methods.module_eval do
    instance_methods.each { |m| undef_method(m) }
  end

  super
end
Instance Protected methods
define_method_attribute(attr_name)

We want to generate the methods via module_eval rather than define_method, because define_method is slower on dispatch and uses more memory (because it creates a closure).

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.

Source: show | on GitHub 

# File activerecord/lib/active_record/attribute_methods/read.rb, line 69
          def define_method_attribute(attr_name)
            generated_attribute_methods.module_eval "              def __temp__
                #{internal_attribute_access_code(attr_name, attribute_cast_code(attr_name))}
              end
              alias_method '#{attr_name}', :__temp__
              undef_method :__temp__
", __FILE__, __LINE__ + 1
          end