Debugging & Best Practices - Learn SpriteBuilder for iOS Game Development - page 463

Listing 14-1 . NSLog used to log when Scroll View delegate methods run
-(void) scrollViewDidEndDragging:(CCScrollView *)scrollView
willDecelerate:(BOOL)decelerate
{
NSLog(@"%@%@", NSStringFromSelector(_cmd), decelerate
? @"YES" : @"NO");
}
Together with the other delegate method's logging, NSLog will print a series of strings to
the Xcode debug console, as seen in Figure 14-1 , when you interact with the Scroll View .
Figure 14-1 . NSLog output in Xcode's debug console after interacting with the level-selection Scroll View
This series of log statements instantly visualizes the flow of execution. You can clearly
see that scrollViewWillBeginDragging: is the first delegate method called,
while scrollViewDidEndDragging with decelerate enabled causes the Scroll View
to continue scrolling past the point where the user stopped dragging. The Scroll View does
so to move the nearest page to its designated position. Once the page has been moved to
its position, the scrolling ends with scrollViewDidEndDecelerating .
Logging is particularly useful if you need to monitor the change of values over time—for
instance, logging the position of a node and its distance to another node in the update
method.
Caution Printing a log line to the console takes time, and printing a long string
with many format specifiers and variables will take longer than a short string. If
you call NSLog once every frame, it may already be enough to show a notice-
able slowdown. So don't forget to remove or comment the NSLog statements
after they've done their job.