Can I use an NSPredicate in Swift with a nil argument?

Question

I\'m trying to convert a project that uses Core Data from Objective-C to Swift.

The data model is structured so that I have one master folder which contains other fo

Answer 1

It looks as if it is (with the current Xcode 6 beta 3 release) generally difficult to pass nil in a variable argument list.

This seems to work:

let predicate = NSPredicate(format: "parentFolder == %@", 0)
print(predicate)
// Output: parentFolder == nil

But the easiest solution would be to simply write the predicate as

NSPredicate(format: "parentFolder == nil")

Answer 2

The easiest solution and fitting for you case would be to simply write the predicate as:

NSPredicate(format: "parentFolder == nil")

But if it is necessary to insert nil as an argument you could use NSNull. This might be useful if you are using an Optional

let folderName: String? = nil
// ... assign folderName if available
NSPredicate(format: "parentFolder == %@", folderName ?? NSNull())

This will result in all folder with the same parent, if the parent is nil, it will fetch all folders without parent.