Switching methods in private classes in Apple frameworks
Switching methods in private classes in Apple frameworks
- Subject: Switching methods in private classes in Apple frameworks
- From: Gideon King <email@hidden>
- Date: Fri, 12 Mar 2010 10:24:08 +1000
(following on from the thread "How to debug this error on closing a document?", but it's really moved on to a new topic at this point)
I was not aware that poseAsClass is not available in 64 bit applications. I looked at the Apple example of exchanging a method in NSWindow, and it looked easy enough, so I tried the method exchanging by using class-dump to generate the header for NSConcreteNotification, and implemented the switch, but it gives a linker error:
"_OBJC_CLASS_$_NSConcreteNotification", referenced from:
l_OBJC_$_CATEGORY_NSConcreteNotification_$_MethodReplacement in MyConcreteNotification.o
__objc_classrefs__DATA@0 in MyConcreteNotification.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
So it must be in the foundation binary, but the linker doesn't pick it up. Is there a way around this?
Gideon
On 12/03/2010, at 2:00 AM, Jerry Krinock wrote:
>
> On 2010 Mar 11, at 02:27, Gideon King wrote:
>
>> or whether I would have to subclass NSConcreteNotification and override dealloc and then use pose as, so I could print out the notification name etc, to get the info
>
> That would work, but Method Replacement [1] was added in Objective-C 2.0 as a replacement for "pose as class". However, to do Method Replacement, you need to declare and implement a category on, in this case NSConcreteNotification, but that won't compile because NSConcreteNotification is Apple-private. Does anyone know how to do Method Replacement for debugging in an Apple-private class?
>
> [1] http://developer.apple.com/mac/library/samplecode/MethodReplacement/index.html
>
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