In the end I think the pain of implementing this seamlessly was not
worth the gain provided.
The intention was that it would allow plain ruby objects that might not
live in your main application to be subclassed and have persistence
mixed in. But I've decided that the benefit of doing that is not worth
the amount of complexity that the implementation introduced.
Selecting which key extensions to include in active_support/rails
made apparent the systematic usage of Object#in? in the code base.
After some discussion in
5ea6b0df9a
we decided to remove it and use plain Ruby, which seems enough
for this particular idiom.
In this commit the refactor has been made case by case. Sometimes
include? is the natural alternative, others a simple || is the
way you actually spell the condition in your head, others a case
statement seems more appropriate. I have chosen the one I liked
the most in each case.
The problem: We need to be able to specify configuration in a way that
can be inherited to models that include ActiveRecord::Model. So it is
no longer sufficient to put 'top level' config on ActiveRecord::Base,
but we do want configuration specified on ActiveRecord::Base and
descendants to continue to work.
So we need something like class_attribute that can be defined on a
module but that is inherited when ActiveRecord::Model is included.
The solution: added ActiveModel::Configuration module which provides a
config_attribute macro. It's a bit specific hence I am not putting this
in Active Support or making it a 'public API' at present.
This fixes a situation I encountered where a subclass would cache the
name of a generated attribute method in @_defined_class_methods. Then,
when the superclass has it's attribute methods undefined, the subclass
would always have to dispatch through method_missing, because the
presence of the attribute in @_defined_class_methods would mean that it
is never generated again, even if undefine_attribute_methods is called
on the subclass.
There various other confusing edge cases like this. STI classes share
columns, so let's just keep all the attribute method generation state
isolated to the base class.
