Archiving, unarchiving and cleaning objects in cache with Swift

Question

I have problems in handling the persistence of some classes in the cache. This is the code I tried and that does not work at all either recovering the archived data or deleting it:

func cacheDirectoryURL()->NSURL?{
    let fileManager=NSFileManager()
    let urls = fileManager.URLsForDirectory(.CachesDirectory, inDomains: .UserDomainMask)
    if urls.count>0{
        return urls[0]
    }
    return nil
}

func palineCacheURL()->NSURL?{
    let url=cacheDirectoryURL()?.URLByAppendingPathExtension("Paline.archive")
    return url
}

public func getMapHandlerWithDelegate(delegate:MovableAnnotationDelegate)->MapDelegate{
    let archiveURL=palineCacheURL()!
    mapHandler=NSKeyedUnarchiver.unarchiveObjectWithFile(archiveURL.absoluteString) as? MapDelegate
    if mapHandler != nil{
        mapHandler!.delegate=delegate;
    } else {
        mapHandler=MapDelegate.sharedMapDelegate()
        mapHandler!.delegate=delegate;
    }
    return mapHandler!
}

func clearMapArchives(){
    do{
        try NSFileManager.defaultManager().removeItemAtPath(palineCacheURL()!.absoluteString);
    } catch let error as NSError {
        print(error.localizedDescription+" "+(error.localizedFailureReason ?? ""));
        let alert=UIAlertView(title:NSLocalizedString("Error", comment:""), message:NSLocalizedString("Unable to clean the cache; please reinstall the app in the case of  problems", comment:""), cancelButtonTitle:NSLocalizedString("Dismiss", comment:""), otherButtonTitle:nil, onDismiss:nil, onCancel:nil)
        alert.show()
    }
}

func archive(){
//-NSLog(@"archivePath=%@ paline=%@", archivePath, self.palineArray);
    if mapHandler != nil {
        NSKeyedArchiver.archiveRootObject(mapHandler!, toFile: palineCacheURL()!.absoluteString)
        print("archivio a \(palineCacheURL()!.absoluteString)")
    }
}

I even tried retrieving the object soon after saving it and it come out nil:

        NSKeyedArchiver.archiveRootObject(mapHandler!, toFile: palineCacheURL().absoluteString)
        print("archivio a \(palineCacheURL().absoluteString)")
        let restored=NSKeyedUnarchiver.unarchiveObjectWithFile(palineCacheURL().absoluteString) as? MapDelegate
        print("restored \(restored)")

Answer 1

Thanking much fluidsonic for the hint, the code was fine with the exception of absoluteString to be replaced with path. Once replaced this part everything work seamlessly.