Another async function

ThenAsyncExampleTask2.swift

func saveToDisk(name:String, image: UIImage, in context: TaskContext) -> Task<NSURL> {
	let task = Task<NSURL>(in: context) { (fullfill, reject) -> (Void) in
		let filemanager = NSFileManager.defaultManager()
		let documentsPath : AnyObject = NSSearchPathForDirectoriesInDomains(.DocumentDirectory,.UserDomainMask,true).first!
		let fPath = documentsPath.stringByAppendingString("/\(name)") as String
		if(!filemanager.fileExistsAtPath(fPath)) {
			guard let data = UIImagePNGRepresentation(image) else {
				reject(Error.Generic(message: "Cannot convert image"))
				return
			}
			do {
				try data.writeToFile(fPath as String, options: NSDataWritingOptions.AtomicWrite)
				fullfill(NSURL(fileURLWithPath: fPath))
			} catch let err as NSError {
				reject(Error.Generic(message: err.localizedDescription))
			}
		} else {
			reject(Error.DuplicateFile(path: fPath))
		}
	}
	return task
}