How does ActiveRecord define methods compared to attr
ActiveRecord seems to define instance methods differently than attr_accessor.
attr_accessor doesn't seem to define a super method for my new defined attribute:
class SomeClass
attr_accessor :some_attribute
def some_attribute
super
end
end
>> some_class = SomeClass.new
>> some_class.some_attribute
NoMethodError: super: no superclass method `some_attribute' for..
Whereas ActiveRecord definitely defines a super method :
class SomeClass < ActiveRecord::Base
# some_attribute is now a column in our database
def some_attribute
super
end
end
>> some_class = SomeClass.new
>> some_class.some_attribute
nil
Where is the difference between both? Is there a way to make attr_accessor define a super method?
EDIT: I still don't know how ActiveRecord defines it's methods, but I know how attr_accessor does it. Instead of super I can use @some_attribute since it stores the values in global variables of the same name: https://stackoverflow.com/a/4371458/586000
When you use attr_accessor in your class that does not inherit from another class, there is, by definition, no method by the same name in a "parent" class. Therefore, super has nowhere to go to find a same-named method. (Well, your class inherits from Object, but Object does not define a method named some_attribute.)
On the other hand, ActiveRecord does define a getter and a setter for your attributes. Therefore, when you define them again in your class (that inherits from ActiveRecord::Base), then Ruby has somewhere to go (ActiveRecord::Base) when you invoke super.
Contrasting attr_accessor and the (many) methods that ActiveRecord generates for your table columns is a bit of an apples and oranges kind of question. ActiveRecord does all sorts of things with the attributes on the underlying table, including--but not limited to--creating getters and setters for the table columns.
(Note on the above: ActiveRecord works mostly by harnessing the power of method_missing, so many or most of the methods defined on your table attributes are actually implemented through the method_missing method. super does in fact invoke method_missing, if it exists, in parent classes, so that is how you can successfully invoke super on some_attribute when you inherit from ActiveRecord::Base.)
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