Problems converting code to Swift from obj-c

Question

Im trying to convert to swift code, which sets files property to "not to backup to iCloud"

Original code looks like this

- (BOOL)addSkipBackupAttributeToItemAtPath:(NSString *) filePathString {
   NSURL* URL= [NSURL fileURLWithPath: filePathString];
   assert([[NSFileManager defaultManager] fileExistsAtPath: [URL path]]);

   NSError *error = nil;
   BOOL success = [URL setResourceValue: [NSNumber numberWithBool: YES]
                              forKey: NSURLIsExcludedFromBackupKey error: &error];
   if(!success){
    NSLog(@"Error excluding %@ from backup %@", [URL lastPathComponent], error);
    }
    return success;
 }

I came with the such code

func addSkipBackupAttributeToItemAtURL(URL: NSURL) -> Bool{

   let fileManager = NSFileManager.defaultManager()
   assert(fileManager.fileExistsAtPath(URL.absoluteString))

   var error:NSError?
   let success:Bool = try? URL.setResourceValue(NSNumber(bool: true),forKey: NSURLIsExcludedFromBackupKey)

   if !success {
    print("Error excluding \(URL.lastPathComponent) from backup \(error)")
   } else {
    print("File at path \(URL) was succesfully updated")
   }

   return success
   }

but it throws error at line with let success:Bool

Cannot convert value of type '()?' to specified type 'Bool'

How to fix that ?

Answer 1

setResourceValue is not returning a Bool to indicate the success, but throws an error when it fails. So you should wrap it in a try catch block.

̶W̶e̶l̶l̶,̶ ̶t̶h̶e̶ ̶d̶o̶c̶u̶m̶e̶n̶t̶a̶t̶i̶o̶n̶ ̶l̶o̶o̶k̶s̶ ̶o̶u̶t̶d̶a̶t̶e̶d̶, the docs describes error handling in Swift at the bottom, but if you jump it's defenition, you would see that the method does not return anything:

public func setResourceValue(value: AnyObject?, forKey key: String) throws