nil is not behaving like nil

[trogdoro]

Whenever I have a one linked association that is empty, the nil value returned is not the correct nil. Normally nil has an object_id equal to 4. This nil has an object_id that is something else. You can emulate the problem by putting the following in your associations spec:

it "should actually be nil" do
  @user.emergency_contact = @friend1
  @user.save

  @friend1.destroy
  @found = User.find(@user.key)
  @found.emergency_contact.object_id.should == nil.object_id
end

This bug renders things like "if" and "unless" useless. Even the && and || operators treat this nil as truthy.

[myronmarston]

This is due to the fact that ripple is using a proxy for the association. It is proxying to nil, but the proxy itself is not nil.

You can check nil with association.nil?.

I agree this is a gotcha, but I'm not sure what the solution should be.

[seancribbs]

Feels like there could be a special-case/guard on the accessor method if the target is nil. That said, .nil? is a good workaround.

[seancribbs]

Another thing I noticed about the snippet is that the target is not actually nil because the link still exists, even though the object on the other side doesn't. There is no referential integrity.

[myronmarston]

Feels like there could be a special-case/guard on the accessor method if the target is nil.

I like this idea. I've used the nil? work around in multiple places and it would be nice to not have to.

I was actually just bitten last night by a bug due to a nil-proxy being truthy. I can take a look at fixing this the next time I'm working on ripple.

One concern, though: once we change the association accessor to return nil, you can't call methods on it anymore (like my_document.my_association.build(:attribute => :hash)--will this potentially break people's apps?

[seancribbs]

@myronmarston I think ActiveRecord went the route of my_document.build_my_association for singular associations.