UIGestureRecognizer and nil-targeted Actions
I like the Cocoa responder chain — I like being able to specify
nil as target and have the action message follow the responder chain until it’s handled (or not).
I like this so much I almost never specify a target — I (just about) always use
But this doesn’t work with
UIGestureRecognizer. The documentation states that “nil is not a valid value” for the target in
If I forget and use nil anyway, nothing happens. (Which is frustrating, because I don’t know why until I remember or look it up. Which just happened.)
How I work around it:
I specify the target in the same file where the gesture recognizer is created. I have it call a method something like this:
rs_performSelectorViaResponderChain looks like this:
I don’t like having to do this, but it works.
Why oh why
But my question is: why does UIGestureRecognizer not take nil as a target and work like everything else works?
I don’t have a theory.
Update 10:30 pm: Chris Parker writes on Twitter:
“They’re intended for specific gestures on views, rather than a hierarchy of actions. More of a virtual control.”
Update June 23, 2012 12:00 pm: Ben Lings asked on Twitter why I didn’t use
-[UIApplication sendAction:to:from:forEvent:] instead of
Excellent question. I think I should be using
sendAction:to:from:forEvent:. So I changed my code.