please anyone tell me how to use sleep() for few milliseconds in swift 2.2?
while (true){
print("sleep for 0.002 seconds.")
sleep(0.002) // not working
}
but
while (true){
print("sleep for 2 seconds.")
sleep(2) // working
}
it is working.
let seconds = UInt64(2)
print("paused at \(Date())")
Task {
do {
try await Task.sleep(nanoseconds: seconds * 1_000_000_000)
print("started again at \(Date()) after \(seconds) seconds")
} catch {
print("An error occurred: \(error.localizedDescription)")
}
}
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usleep() takes millionths of a second
usleep(1000000) //will sleep for 1 second
usleep(2000) //will sleep for .002 seconds
OR
let ms = 1000
usleep(useconds_t(2 * ms)) //will sleep for 2 milliseconds (.002 seconds)
OR
let second: Double = 1000000
usleep(useconds_t(0.002 * second)) //will sleep for 2 milliseconds (.002 seconds)
usleep(UInt32(0.002 * second))
man sleep on macOS 11.6 says: "The usleep() function is obsolescent. Use nanosleep(2) instead."I think more elegant than usleep solution in current swift syntax is:
Thread.sleep(forTimeInterval: 0.002)
sleep(forTimeInterval:) just call nanosleep()?
nanosleep is a system function, part of Darwin, and Thread is part of Foundation. It may happen that in the older versions of iOS/macOS it was using usleep under the hood, and now it may be using nanosleep. Anyway you don't need to use nanosleep when you can import Foundation, it may only be needed for other languages which cannot use Foundation, but still have access to Darwin, as it's written in C.use func usleep(_: useconds_t) -> Int32 (import Darwin or Foundation ...)
IMPORTANT: usleep() takes millionths of a second, so usleep(1000000) will sleep for 1 sec
If you really need to sleep, try usleepas suggested in @user3441734's answer.
However, you may wish to consider whether sleep is the best option: it is like a pause button, and the app will be frozen and unresponsive while it is running.
You may wish to use NSTimer.
//Declare the timer
var timer = NSTimer.scheduledTimerWithTimeInterval(0.002, target: self, selector: #selector(MyClass.update), userInfo: nil, repeats: true)
self, selector: "update", userInfo: nil, repeats: true)
func update() {
// Code here
}
usleep in a high-level part of your app. It can block GCD queues, for one. Only use if the abstractions Apple provides really aren't suitable for what you need to do.DispatchQueue.global(qos: .background).async {
let second: Double = 1000000
usleep(useconds_t(0.002 * second))
print("Active after 0.002 sec, and doesn't block main")
DispatchQueue.main.async{
//do stuff in the main thread here
}
}
DispatchQueue.main.asyncAfter(deadline: .now() + 0.002) {
/*Do something after 0.002 seconds have passed*/
}
dTime without of destroying previous threads. So in better case you waste device's memory, in worst case the app falls due to huge memory consumption (depends on loop count)For Example Change Button Alpha Value
sender.alpha = 0.5
DispatchQueue.main.asyncAfter(deadline:.now() + 0.2){
sender.alpha = 1.0
}
