Timer extension to add basic block timers for pre-iOS 10.

TimerExtensions.swift

public extension Timer {
    
    @discardableResult
    public class func scheduledTimer(withTimeInterval interval: TimeInterval, block: @escaping (Timer) -> Void) -> Timer {
        
        let fireDate = interval + CFAbsoluteTimeGetCurrent()
        let timer = CFRunLoopTimerCreateWithHandler(kCFAllocatorDefault, fireDate, 0, 0, 0) { (runLoopTimer) in
            block(runLoopTimer!)
        }!
        CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, CFRunLoopMode.commonModes)
        return timer
    }
}