unrecognized selector with category NSMutableData - objective-c

Question

I'm adding a category to NSData as follows:
// PacketCategories.h
#interface NSData(PacketSplit)
- (NSArray *)splitTransferredPackets:(NSData **)leftover;
#end
// PacketCategories.m
#implementation NSData(PacketSplit)
- (NSArray *)splitTransferredPackets:(NSData **)leftover {
NSMutableArray *ret = [NSMutableArray array];
const unsigned char *beginning = [self bytes];
const unsigned char *offset = [self bytes];
NSInteger bytesEnd = (NSInteger)offset + [self length];
while ((NSInteger)offset < bytesEnd) {
uint64_t dataSize[1];
NSInteger dataSizeStart = offset - beginning;
NSInteger dataStart = dataSizeStart + sizeof(uint64_t);
NSRange headerRange = NSMakeRange(dataSizeStart, sizeof(uint64_t));
[self getBytes:dataSize range:headerRange];
if (dataStart + dataSize[0] + (NSInteger)offset > bytesEnd) {
NSInteger lengthOfRemainingData = [self length] - dataSizeStart;
NSRange dataRange = NSMakeRange(dataSizeStart, lengthOfRemainingData);
*leftover = [self subdataWithRange:dataRange];
return ret;
}
NSRange dataRange = NSMakeRange(dataStart, dataSize[0]);
NSData *parsedData = [self subdataWithRange:dataRange];
[ret addObject:parsedData];
offset = offset + dataSize[0] + sizeof(uint64_t);
}
return ret;
}
#end
And then trying to call that category:
#import "PacketCategories.h"
NSMutableData *data = [NSMutableData data];
// Read some data
[data appendBytes:buffer length:bytesRead];
NSArray *dataPackets = [data splitTransferredPackets:&readLeftover];
Which gets the following error:
-[NSConcreteMutableData splitTransferredPackets:]: unrecognized selector sent to instance 0x6e6f7b0
[ERROR] The application has crashed with an unhandled exception. Stack trace:
Any ideas? Does NSConcreteMutableData not inherit from NSData?
Other suggested answers (Objective-C Category Causing unrecognized selector) have suggested that the file isn't linked in, which is not possible because other categories defined in this file are used just fine.
Thanks

Answer 1

Ookay. I had the same problem, but with a different outcome. Briefly, the problem was in my project file. The category files showed up in the project navigator - I can load/edit, etc. But the linker did not know to link with them. The way I found this was pulling on another thread - creating a dummy concrete class in my category files to force the linker to include them. No luck. Then I tried to instantiate an instance of the dummy class in my app. Eureka - I now get a linker error! So, I simply removed and re-added the category files to the project and now all is well. Not sure how the project file got out of whack ( svn merge? ), but there it is.

Answer 2

Delete the Category files and add them again checking the target.
Solved for me.