Test code for checking DispatchQueue.getSpecific method

DispatchQueue_getSpecific_test.swift

final class Test {
    private let queue: DispatchQueue
    private let queueKey : DispatchSpecificKey<Int>
    private let queueKeyValue: Int
    
    init() {
        let queueKey = DispatchSpecificKey<Int>()
        let queueKeyValue = Int(arc4random())
        
        self.queueKey = queueKey
        self.queueKeyValue = queueKeyValue
        
        queue = .init(label: "custom.queue") //.global(qos: .background)
        queue.setSpecific(key: queueKey, value: queueKeyValue)
    }
    
    func testQueue() {
        func check(inQueue flag: Bool) {
            debugPrint(#function +  " in queue \(flag)")
            guard checkIfInQueue() == flag else {
                assertionFailure("Failed in queue \(flag)")
                return
            }
            debugPrint("Called flag \(flag)")
        }
        
        DispatchQueue.main.async(execute: { check(inQueue: false) })
        
        runOnQueue { check(inQueue: true) }
        
        //Thread.isMainThread
    }
    
    private func checkIfInQueue() -> Bool {
        DispatchQueue.getSpecific(key: queueKey) == queueKeyValue
    }
    
    private func runOnQueue(_ block: @escaping () -> Void,
                            dispatchSynch: Bool = false) {
        let tempBlock: ( Bool ) -> Void = { [weak self] smartSync in
            if smartSync {
                block()
            } else if dispatchSynch {
                self?.queue.sync(execute: block)
            } else {
                self?.queue.async(execute: block)
            }
        }
        tempBlock(checkIfInQueue())
    }
}

let x = Test()
x.testQueue()


/*
 void *xmppQueueTag;
 
 - (void) init {
    // ......
    xmppQueueTag = &xmppQueueTag;
    xmppQueue = dispatch_queue_create("xmpp", DISPATCH_QUEUE_SERIAL);
    dispatch_queue_set_specific(xmppQueue, xmppQueueTag, xmppQueueTag, NULL);
 }
 
 - (void) run {
    // ......
    if (dispatch_get_specific(xmppQueueTag))
        block();
    else
        dispatch_sync(xmppQueue, block);
 }

 */