Swift - Dispatch Queues and the U/I running serially - swift

Question

I have a secondary LaunchScreenViewController for an App that has some animation whilst it gathers three types of background data.
Everything works but the order in which the DispatchQueues.async are run is random. However if I change them to DispatchQueues.sync everything happens in the right order but runs so fast (even with sleeps) you don't see the animations.
This needs to be .sync but how do I control the U/I so that I can see the animation? (Shown here as, e.g. self.subLogo1View.isHidden = true)
Here's the code:
// Queuing Variables
var semaphore = DispatchSemaphore(value: 1)
var semaphoreSub = DispatchSemaphore(value: 1)
override func viewDidLoad() {
super.viewDidLoad()
DispatchQueue.global().async {
self.semaphore.wait()
self.gatherData()
self.semaphore.signal()
}
DispatchQueue.global().async {
self.semaphore.wait()
self.checkNetworkAvailability()
self.semaphore.signal()
}
DispatchQueue.global().async {
self.semaphore.wait()
self.checkSomething()
self.semaphore.signal()
}
}
func gatherData() {
DispatchQueue.main.async {
self.semaphoreSub.wait()
print ("1")
self.subLogo1View.isHidden = true
self.subLogo1View.setNeedsDisplay()
self.semaphoreSub.signal()
}
}
func checkNetworkAvailability() {
DispatchQueue.main.async {
self.semaphoreSub.wait()
print ("2")
self.subLogo2View.isHidden = true
self.subLogo2View.setNeedsDisplay()
self.semaphoreSub.signal()
}
}
func checkSomething() {
DispatchQueue.main.async {
self.semaphoreSub.wait()
print ("3")
self.subLogo3View.isHidden = true
self.subLogo3View.setNeedsDisplay()
self.semaphoreSub.signal()
}
}

Answer 1

Instead of manually serializing your closures with a bunch of semaphores, you maybe better use a custom serial queue. For animation, user UIView.animate
Something like this:
func gatherData() {
DispatchQueue.main.async { // or sync, depending on your animation needs
print ("1: gather Data")
UIView.animate(withDuration: 0.5) {
self.subLogo1View.alpha = 0 // instead of isHidden
}
}
}
func viewDidLoad() {
var mySerialQueue = DispatchQueue (label:"my.serial")
mySerialQueue.async {
self.gatherData()
}
mySerialQueue.async {
self.checkNetworkAvailability()
}
// ...
}