Fix request descriptor lookup class matching.

[deanbrowne]

Class matching was done based on address equality of the Class.
Almost always that is enough, but two different Class structs can be
created to represent the same thing. When this happens RestKit could
not match the registered RequestDescriptor.

This happened to me and I have no way to create a good reproducable
test. I found a [StackOverflow
thread](http://stackoverflow.com/questions/16424298/why-is-class-nsclass
fromstringnsstringfromclass-class-on-os-x) on this happening.

[segiddins]

@deanbrowne before we think about merging this, could you please add a failing unit test? Thanks

[deanbrowne]

Could not make one. As I pointed out in the comments it is pretty weird to
get 2 different Class structs. It only happened to me in one of my unit
tests and I was unable to figure out why it worked in my app's code, worked
in most of tests, but no in just one.

On Fri, Nov 29, 2013 at 4:13 PM, segiddins notifications@github.com wrote:

@deanbrowne https://github.com/deanbrowne before we think about merging
this, could you please add a failing unit test? Thanks

—
Reply to this email directly or view it on GitHubhttps://github.com//pull/1692#issuecomment-29542272
.

[segiddins]

@deanbrowne without a failing test, I'm hesitant to merge in any changes

[percysnoodle]

@deanbrowne I had a problem a few weeks ago, not related to RestKit, where I'd accidentally added a .m file from one of my pods to my main target, and so I had two copies of the same class, and it was causing weird problems in places where I was calling isKindOfClass:. Perhaps something similar happened to you with your unit tests?

I'm not sure testing by class name is the best way of checking for this, though; it seems to me that having two classes with the same name but different implementations is just as likely as having two copies of the same class, if not more so.

[percysnoodle]

@deanbrowne if you want to write a test for multiple classes with the same name, have a look at objc_allocateClassPair and objc_registerClassPair - there's an example of them in use here.

[blakewatters]

Comparing classes should be sufficient. This probably indicates that you actually have two copies of the class compiled in somehow and are getting different versions randomly. This can happen if you compile one into a static library/testing bundle and another copy into the main app target.

I believe this to be an issue on the user side and do not want to merge any changes.