NSMultipleValuesMarker use of undeclared type in Swift 3

Question

I'm working on a mixed Objective-C / Swift macOS app.

I'm writing some code that checks the value returned from the selection key on an arrayController. NSArrayControllers return Any and normally I would check for multiple selection by seeing if the Any is a NSMultipleValuesMarker. However, writing this in Swift 3 I get the error:

Use of undeclared type 'NSMultipleValuesMarker'

The code I'm attempting is:

    var selection = arrayController.value(forKeyPath: "selection.image")

    if selection is NSMultipleValuesMarker {
        // Do something for this case
    }

I can't figure out what I'm missing to have NSMultipleValuesMarker available. I've tried importing Foundation, Cocoa and AppKit, but none of them seem to make the error go away.

Answer 1

'is' is the type check operator to check whether an instance is of a certain subclass type. Use selection === NSMultipleValuesMarker to check if selection is NSMultipleValuesMarker.