AR Association Proxy prevents calling methods defined using method_missing on the target of the association

HI all,

I've created a ticket
https://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/3481-ar-association-proxy-prevents-calling-methods-defined-using-method_missing-on-the-target-of-the-association
for this problem and a patch if someone would like to pick it up. Is
this the correct procedure for assigning a ticket? :stuck_out_tongue:

From the commit:

Don't raise a NoMethodError if the target does not respond_to? method.
This excludes methods on target that are implemented using
method_missing. And if the method really doesn't exist, target.send
(method, args) will raise a NoMethodError itself...so let it do that.

Description:

If I have a model like this:

class User < ActiveRecord::Base
# Provide is_admin?, is_guest? account type discovery methods def
method_missing(method_id, *arguments)
if match = /^is_(\w+)\?$/.match(method_id.to_s)
  self.account_type == match[1]
else
  super
end

end end

class Activity < ActiveRecord::Base
belongs_to :user end

I can't do Activity.first.user.is_guest? because it raises a
NoMethodError. The problem is that the Association Proxy only allows
calling methods on the target that respond_to?(method). It doesn't
need to do this check, because if the method really doesn't exist, the
call to target.send(method, args) will raise NoMethodError itself, so
nothing is gained by doing that check in the proxy.

Regards,
Karl

If I have a model like this:

class User < ActiveRecord::Base
# Provide is_admin?, is_guest? account type discovery methods def
method_missing(method_id, *arguments)
if match = /^is_(\w+)\?$/.match(method_id.to_s)
self.account_type == match[1]
else
super
end

end end

If you override method_missing, you need to also override respond_to?

I can't do Activity.first.user.is_guest? because it raises a
NoMethodError. The problem is that the Association Proxy only allows
calling methods on the target that respond_to?(method). It doesn't
need to do this check, because if the method really doesn't exist, the
call to target.send(method, args) will raise NoMethodError itself, so
nothing is gained by doing that check in the proxy.

This is not quite right. send will also call private methods, the
proxy check prevents that.