Mutex alternatives in swift

Thanks to beshio's comment, you can use semaphore like this:

let semaphore = DispatchSemaphore(value: 1)

use wait before using the resource:

semaphore.wait()
// use the resource

and after using release it:

semaphore.signal()

Do this in each thread.

There are many solutions for this but I use serial queues for this kind of action:

let serialQueue = DispatchQueue(label: "queuename")
serialQueue.sync { 
    //call some code here, I pass here a closure from a method
}

Edit/Update: Also for semaphores:

let higherPriority = DispatchQueue.global(qos: .userInitiated)
let lowerPriority = DispatchQueue.global(qos: .utility)

let semaphore = DispatchSemaphore(value: 1)

func letUsPrint(queue: DispatchQueue, symbol: String) {
    queue.async {
        debugPrint("\(symbol) -- waiting")
        semaphore.wait()  // requesting the resource

        for i in 0...10 {
            print(symbol, i)
        }

        debugPrint("\(symbol) -- signal")
        semaphore.signal() // releasing the resource
    }
}

letUsPrint(queue: lowerPriority, symbol: "Low Priority Queue Work")
letUsPrint(queue: higherPriority, symbol: "High Priority Queue Work")

RunLoop.main.run()