A drop-in Swift replacement for NSTimer: faster and lighter weight using GCD

DRTimer.swift

//  DRTimer.swift
//  ConfusionUtilFramework
//
//  Created by dan on 5/4/17.
//  Copyright © 2017 Confusion Studios LLC. All rights reserved.
//
import UIKit

// a faster timer than NSTimer, drop in replacement for
// just one of the methods... it's not precise but it works...
@objc(DRTimer)
open class DRTimer : NSObject {

    static var queue:DispatchQueue = DispatchQueue(label: "com.dr2050.DRTimer", attributes: .concurrent)
    var timer: DispatchSourceTimer!
    open var userInfo:Any?

    // most code is from here: http://stackoverflow.com/a/39581096/8047
    // NOTE: repeats is always true... if you don't want a repeating timer, use
    // dispatch_after
    open class func scheduledTimer(timeInterval ti: TimeInterval, target aTarget: Any, selector aSelector: Selector, userInfo:Any?=nil) -> DRTimer {
        let retVal = DRTimer()
        let timer = DispatchSource.makeTimerSource(queue: DRTimer.queue)
        retVal.timer = timer
        retVal.userInfo = userInfo
        let microseconds = Int(ti * 1000000)
        timer.scheduleRepeating(deadline: .now(), interval: .microseconds(microseconds))

        timer.setEventHandler {
            if let target = aTarget as? NSObject {
                target.perform(aSelector, with: retVal)
            }
        }

        timer.resume()
        return retVal
    }

    open var isValid:Bool {
        guard let timer = timer else { return false }
        return !timer.isCancelled
    }

    open func invalidate() {
        timer?.cancel()
        userInfo = nil
        timer = nil
    }

    deinit {
        invalidate()
    }
}