An example of overloaded functions in Swift. - More explanation at http://abizern.org/2015/10/11/swift-function-overloading-by-return-type/

Timer.swift

//: Playground - noun: a place where people can play

import Foundation
import XCPlayground

XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

// Extend NSTimeInterval to provide the conversion functions.
extension NSTimeInterval {

    var nSecMultiplier: Double {
        return Double(NSEC_PER_SEC)
    }

    public func nSecs() -> Int64 {
        return Int64(self * nSecMultiplier)
    }

    public func nSecs() -> UInt64 {
        return UInt64(self * nSecMultiplier)
    }

    public func dispatchTime() -> dispatch_time_t {
        // Since the last parameter takes an Int64, the version that returns an Int64 is used.
        return dispatch_time(DISPATCH_TIME_NOW, self.nSecs())
    }
}


// Define a simple function for getting a timer dispatch source.
func repeatingTimerWithInterval(interval: NSTimeInterval, leeway: NSTimeInterval, action: dispatch_block_t) -> dispatch_source_t {

    let timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue())
    guard timer != nil else { fatalError() }

    dispatch_source_set_event_handler(timer, action)
    // This function takes the UInt64 for the last two parameters
    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, interval.nSecs(), leeway.nSecs())

    dispatch_resume(timer)

    return timer
}

// Create the timer
let timer = repeatingTimerWithInterval(1, leeway: 0.1) { () -> Void in
    print("Hello!")
}

// Turn off the timer after a few seconds
dispatch_after(3.0.dispatchTime(), dispatch_get_main_queue()) { () -> Void in
    dispatch_source_cancel(timer)
}

Updated to using a calculated property for the multiplier rather than a static, and the newer method of setting a playground to run indefinitely.