debounce in Swift 3

debounce.swift

func debounce(delay: Int, queue: DispatchQueue, action: (()->()) ) -> ()->() {
	  var lastFireTime   = DispatchTime.now()
	  let dispatchDelay  = DispatchTimeInterval.seconds(delay)

	  return {
		    lastFireTime     = DispatchTime.now()
            let dispatchTime: DispatchTime = lastFireTime + dispatchDelay
		    queue.after(when: dispatchTime) {
				           let when: DispatchTime = lastFireTime + dispatchDelay
				           let now = DispatchTime.now()
				           if now.rawValue >= when.rawValue {
					             action()
				           }
			         }
	         }
}

func testDebounce() {
    print(DispatchTime.now())
    let queue = DispatchQueue.global(attributes: .qosDefault)
    for i in [0...9] {
    debounce(delay: 1, queue: queue, action: {
                 print(DispatchTime.now())
                 print("Fired")
    })()
    }

    Thread.sleep(forTimeInterval: 2)
    print(DispatchTime.now())
}

Note that queue.after(when:) has actually been renamed to queue.asyncAfter(deadline:). And closure arguments are non-escaping by default now, so you need to add a @escaping:

public func debounce(delay: Int, queue: DispatchQueue = .main, action: @escaping (()->())) -> ()->() {
    var lastFireTime  = DispatchTime.now()
    let dispatchDelay = DispatchTimeInterval.seconds(delay)

    return {
        lastFireTime = DispatchTime.now()
        let dispatchTime: DispatchTime = lastFireTime + dispatchDelay

        queue.asyncAfter(deadline: dispatchTime) {
            let when: DispatchTime = lastFireTime + dispatchDelay
            let now = DispatchTime.now()
            if now.rawValue >= when.rawValue {
                action()
            }
        }
    }
}