ios - Cancelling a DispatchWorkItem waiting for execution in DispatchQueue -

what trying achieve:

i trying execute 2 different tasks depending on if user tapped screen once or twice in touchesbegan method.

in process of doing so, delaying execution of singletaptask 0.3s able cancel dispatchworkitem belonging doubletaptask.

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my approach:

override func touchesbegan(_ touches: set<uitouch>, event: uievent?) {     touch in touches {          let singletaptask = dispatchworkitem {             // single tap         }         let doubletaptask = dispatchworkitem {             // double tap         }          if touch.tapcount == 1 {             dispatchqueue.main.asyncafter(deadline: .now() + 0.3, execute: singletaptask)          } else if touch.tapcount == 2 {             singletaptask.cancel()             dispatchqueue.main.async(execute: doubletaptask)          }     } } 

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issue:

for reason singletaptask still executed alongside doubletaptask though singletaptask has been canceled. can not figure out why singletaptask executed in first place , highly appreciate :)

a simple approach add 2 uitapgesturerecognizer view (singletapgesturerecognizer , doubletapgesturerecognizer).

the first 1 configured singletapgesturerecognizer.numberoftapsrequired = 1, second 1 doubletapgesturerecognizer.numberoftapsrequired = 2.

now add singletapgesturerecognizer.require(tofail: singletapgesturerecognizer)

furthermore, approach above not targeting sequential single , double taps, number of taps @ 1 tap (number of fingers tapping @ same time)