Why can't files in my iPhone NSBundle folder be deleted?

I'm having trouble figuring out why files in my iPhone app seem to persist, even when I've deleted them. Here's the code that's giving me trouble:

开发者_如何学GoNSFileManager *fileManager = [NSFileManager defaultManager];
NSString *bundlePath = [[NSBundle mainBundle] bundlePath];
NSString *folderPath = [bundlePath stringByAppendingPathComponent:@"filefolder"];
NSArray *fileNames = [fileManager contentsOfDirectoryAtPath:folderPath error:NULL];

This code is supposed to look at the folder "filefolder" and read its contents into fileNames. When I run this app the very first time, it will do this. But if I change the contents of filefolder (for instance if I add or delete files) and I build and run the app again, the array filenames will contain names of all the newly added files (good) but also contains names of all the files that were supposed to have been deleted (bad)!!

Can anyone help me understand why I'm seeing this behavior?

Did you do a "Clean" in XCode after adding/removing new items from the bundle? This usually solves the problem of "stale" resources.