invoke_numberOfRowsInColumn.mm

NSInteger column = 2;
SEL sel = NSSelectorFromString(@"numberOfRowsInColumn:");
NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[datePickerView methodSignatureForSelector:sel]];
[inv setSelector:sel];
[inv setTarget:datePickerView];
[inv setArgument:&column atIndex:2];
[inv invoke];
NSUInteger length = [[inv methodSignature] methodReturnLength];
NSInteger buffer = (NSInteger)malloc(length);
[inv getReturnValue:&buffer];