Check if Protocol Method is Defined

Question

UIScrollViewDelegate has a new awesome method:

// called on finger up if the user dragged. velocity is in points/second. targetContentOffset may be changed to adjust where the scroll view comes to rest. not called when pagingEnabled is YES
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView 
                     withVelocity:(CGPoint)velocity 
              targetContentOffset:(inout CGPoint *)targetContentOffset __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_5_0)

However, this is ONLY available in iOS 5. For iOS's without this method, I'd like to use paging as an alternative. So I'm left with two options:

1. Check the iOS version, which I don't know how to do, or
2. Check to see if this method is defined for the UIScrollViewDelegate protocol, which I also don't know how to do.

I would prefer to somehow check if the method is defined in the protocol rather than checking the iOS version. Note that doing a respondsToSelector: check won't be adequate since my class implementing the protocol will always define it.

Answer 1

BOOL isAtLeastIOS5 = [[[UIDevice currentDevice] systemVersion] floatValue] >= 5.0;

See How to test a protocol for a method? to test the protocol for a given method.