#import int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; NSSet* set = [NSSet setWithArray:@[@1,@"hello",@2,@"world"]]; NSMutableSet* mutable = [NSMutableSet setWithCapacity:5]; [mutable addObject:@1]; [mutable addObject:@2]; [mutable addObject:@3]; [mutable addObject:@4]; [mutable addObject:@5]; [mutable addObject:[NSURL URLWithString:@"www.apple.com"]]; [mutable addObject:@[@1,@2,@3]]; [mutable unionSet:set]; [mutable removeAllObjects]; // Set break point at this line. [mutable unionSet:set]; [mutable addObject:@1]; [pool drain]; return 0; }