Comparing AnyObject in Swift - objective-c

Question

I'm having trouble porting this Objective-C code to Swift. The code must sort the contents of a directory by a given property.
NSArray *contents = [fileManager contentsOfDirectoryAtURL:directoryURL includingPropertiesForKeys:#[property] options:kNilOptions error:&error];
if (!contents) return nil;
contents = [contents sortedArrayUsingComparator:^NSComparisonResult(NSURL *url1, NSURL *url2) {
id value1;
if ([url1 getResourceValue:&value1 forKey:property error:nil]) return NSOrderedAscending;
id value2;
if ([url2 getResourceValue:&value2 forKey:property error:nil]) return NSOrderedDescending;
return [value1 compare:value2];
}];
return contents
My Swift version so far:
if let contents = fileManager.contentsOfDirectoryAtURL(directoryURL, includingPropertiesForKeys: [property], options: NSDirectoryEnumerationOptions.allZeros, error: &error) as? [NSURL] {
let sortedContents = contents.sorted({(URL1 : NSURL, URL2 : NSURL) -> Bool in
var value1 : AnyObject?
if !URL1.getResourceValue(&value1, forKey: property, error: nil) { return true }
var value2 : AnyObject?
if !URL2.getResourceValue(&value2, forKey: property, error: nil) { return false }
// How do I compare AnyObject?
return false
})
return sortedContents
} else {
return nil
}
Particularly, I don't know how to compare two AnyObject objects. I can't downcast to the Comparable protocol because it's not marked as #objc and apparently I can't call compare with optional chaining syntax (error: Operand of postfix '?' should have optional type; type is 'NSComparisonResult').
Of course, there's always the brute-force approach of downcasting the values to String, NSDate and NSNumber:
if let string1 = value1 as? String {
if let string2 = value2 as? String {
return string1 < string2
}
}
if let date1 = value1 as? NSDate {
if let date2 = value2 as? NSDate {
return date1.compare(date2) == NSComparisonResult.OrderedAscending
}
}
// And so on...
return false
Is there a better way?

Answer 1

Unless they really are AnyObject (ie., they can be swift things) declare them (or cast them) to NSObject instead.

Answer 2

The problem is not with the receiver type of AnyObject (that is fine; you can call any known objc method with AnyObject); but with the parameter type. There is no single signature of compare:. There's one that takes NSString; one that takes NSNumber; one that takes NSDate, etc., but none that is general, none that takes AnyObject.