An extension of NSURLSession showcasing how its functionality could be wrapped in Futures

NSURLSession+FutureProof.swift

extension NSURLSession {
    func fetch(url: String) -> Async<Result<(NSData, NSURLResponse), Error>> {
        return Async { completion in
            let task = self.dataTaskWithURL(NSURL(string: url)!, completionHandler: { (data, response, error) -> Void in
                if let data = data, response = response {
                    completion(Result(value: (data, response)))
                } else {
                    completion(Result(error: .LegacyError(error)))
                }
            })
            task.resume()
        }
    }
}