在Ruby中使用模块扩展对象时的奇怪行为

Question

If I do the following:

user = User.new
user.extend Customer
user.is_a? Customer == true

it works fine.

However if I do the following (where Profile is a mongoid model and user is embedded):

profile = Profile.all.first
profile.user.extend Customer
profile.user.is_a? Customer == false

user is no longer a customer. There must be a simple reason for this but I can't see it.

Edit: User and Profile are mongoid Models, ie. profile.user.class = User and profile.class = Profile.

Answer 1

My guess: every time you call profile.user you are getting a new object. Try:

2.times{ p profiler.user.object_id }

and see what happens. Then try:

u = profile.user
u.extend Customer
p u.is_a? Customer
p profile.user.is_a? Customer

and see what output you get.

Answer 2

This actually ended up being a bug in Mongoid. Here is the issue with description: https://github.com/mongoid/mongoid/issues/1933

It is now fixed in the latest commit.