queue

queue.swift

@IBAction func printHello(_ sender: Any) {
    // 队列，以消息绑定为例
    if shouldWaitSwitch.isOn {
        while true {
            let isSuccess = WaitingTaskQueue.append(task: "你好！")
            if isSuccess { break } else { continue }
        }
        
        if let _ = shouldWaitSwitch.actions(forTarget: WaitingTaskQueue.self, forControlEvent: .valueChanged) { // already set
            return
        }

        shouldWaitSwitch.addTarget(WaitingTaskQueue.self, action: #selector(WaitingTaskQueue.dealingTasks), for: .valueChanged)
    }
    else {
        print("你好！")
        
        if let _ = shouldWaitSwitch.actions(forTarget: WaitingTaskQueue.self, forControlEvent: .valueChanged) { // if set
            shouldWaitSwitch.removeTarget(WaitingTaskQueue.self, action: #selector(WaitingTaskQueue.dealingTasks), for: .valueChanged)
        }
    }
}

@IBOutlet weak var shouldWaitSwitch: UISwitch!

class WaitingTaskQueue {
    private static var firstItemPosition = 0
    private static var queue:[String] = []
    private static var isLocked = false
    
    @objc static func dealingTasks() {
        guard !isLocked else {
            return
        }
        
        isLocked = true
        
        var relativePosition = 0
        while relativePosition < queue.count {
            print("\(queue[relativePosition]), \(firstItemPosition + relativePosition)")
            relativePosition += 1
        }
        queue.removeAll(keepingCapacity: true)
        firstItemPosition += relativePosition
        
        isLocked = false
    }
    
    static func append(task:String) -> Bool { // is success
        guard !isLocked else {
            return false
        }
        
        queue.append(task)
        
        return true
    }
}