Note: This is not duplicate question I have already seen Dispatch group - cannot notify to main thread
There is nothing answered about DispatchWorkItem
I have code like below
let dwi3 = DispatchWorkItem {
print("start DispatchWorkItem \(Thread.isMainThread)")
sleep(2)
print("end DispatchWorkItem")
}
let myDq = DispatchQueue(label: "A custom dispatch queue")
dwi3.notify(queue: myDq) {
print("notify")
}
DispatchQueue.global().async(execute: dwi3)
Which is working correctly (I can see notify on console) and not in main thread start DispatchWorkItem false
start DispatchWorkItem false
end DispatchWorkItem
notify
Now I am trying to notify to main thread using
dwi3.notify(queue: DispatchQueue.main) {
print("notify")
}
But it never calls , I have read and found that if Thread is blocked then situation occurs. but i am already executing DisptachWorkItem
in DispatchQueue.global()
Please Anyone can help me on this that what actually going on ?
If you are running asynchronous code in a playground then you need to enable indefinite execution, otherwise execution may end before the callbacks execute.
Add the following lines to your code in the playground:
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true
Once you do this, you will see that the notify executes correctly on the main queue.
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