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
28:         def cache_attribute?(attr_name)
29:           cached_attributes.include?(attr_name)
30:         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
17:         def cache_attributes(*attribute_names)
18:           cached_attributes.merge attribute_names.map { |attr| attr.to_s }
19:         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
23:         def cached_attributes
24:           @cached_attributes ||= columns.select { |c| cacheable_column?(c) }.map { |col| col.name }.to_set
25:         end
undefine_attribute_methods()

Source: show | on GitHub 

    # File activerecord/lib/active_record/attribute_methods/read.rb, line 32
32:         def undefine_attribute_methods
33:           generated_external_attribute_methods.module_eval do
34:             instance_methods.each { |m| undef_method(m) }
35:           end
36: 
37:           super
38:         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
69:           def define_method_attribute(attr_name)
70:             generated_attribute_methods.module_eval "def __temp__\n\#{internal_attribute_access_code(attr_name, attribute_cast_code(attr_name))}\nend\nalias_method '\#{attr_name}', :__temp__\nundef_method :__temp__\n", __FILE__, __LINE__ + 1
71:           end