Resetting DispatchQueue each time a tap occurs - ios

Question

I have a simple app that is intended to work like this:
App loads with a default image
Once a tap is received a random image is loaded from list
If no tap is received for 5 seconds we reset back to default image
I'm attempting to accomplish this using DispatchQueue and DispatchWorkItem. I have managed to get the above functionality working - except when a user is tapping multiple times.
I'm assuming this is because we are initiating the "resetToOff" DispatchWorkItem each time we tap without resetting the 5 seconds.
How do I reset the image back to the default image if there is no touch received for 5 seconds while resetting the DispatchQueue?
Here is what I have so far:
import SwiftUI
struct PlayView : View {
#ObservedObject var viewRouter: ViewRouter
#State var imageName : String = "smiley"
var body: some View {
ZStack {
Color.black
.edgesIgnoringSafeArea(.all)
Image(imageName)
}
.gesture(
TapGesture()
.onEnded {
let resetToOff = DispatchWorkItem {
self.imageName = "smiley"
}
self.changeImage()
DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(5), execute: resetToOff)
}
)
// Activate the options menu
.onLongPressGesture(minimumDuration: 3) {
self.viewRouter.currentPage = "menuView"
}
}
func changeImage() {
let tempImageName : String = self.imageName
let list : Array = [
"smileyPink",
"smileyGreen",
"smileyRed",
"smileyBlue",
"smileyYellow"
]
self.imageName = list.randomElement() ?? ""
// Ensure that new image selection is not the same as previous image
while tempImageName == self.imageName {
self.imageName = list.randomElement() ?? ""
}
}
}
struct PlayView_Previews : PreviewProvider {
static var previews: some View {
PlayView(viewRouter: ViewRouter())
}
}
Any help with this would be much appreciated.

Answer 1

I think it's really easy to modify your code so that resetToOff only does something if 5 or more seconds passed from last tap:
var lastTapped: DispatchTime
...
.gesture(
TapGesture()
.onEnded {
lastTapped = DispatchTime.now() // remember the time of last tap
and then:
let resetToOff = DispatchWorkItem {
if self.lastTapped + .seconds(5) <= DispatchTime.now() { // 5 sec passed from last tap
self.imageName = "smiley"
} // otherwise do nothing
}
Since both setting and modifying lastTapped happens on main thread, it's thread safe. Of course it means you potentially adding "no work needed" item to main queue, but it's likely a very low impact.

Answer 2

It would be simpler to use a Timer, because that is something that is easy to cancel (invalidate) and start the timer again (Timer.scheduledTimer) if the user taps before the Timer fires at the end of 5 seconds.
For example, that is how my LinkSame app works. There is a 10-second "move" timer. If the user doesn't make a valid move within 10 seconds of the previous move, the user loses 10 points and the timer starts over. If the user does make a valid move within 10 seconds of the previous move, the user gets a score based on where we are in the timer and the timer starts over. That is all accomplished with a Timer.