Swift 4: Bitwise AND for NSEvent.modifierFlags [duplicate]

Question

I'm trying to set up a hotkey (option-tab) using NSEvent.addGlobalMonitorForEvents

let keycode = 48 // tab
let keymask: NSEvent.ModifierFlags = .option

func handler(event: NSEvent!) {

    if event.keyCode == keycode && 
        event.modifierFlags == event.modifierFlags & keymask     {

        // do whatever

    }
}

NSEvent.addGlobalMonitorForEvents(matching: [.keyDown], handler: handler)

But I get this error in the bitwise AND part:

Cannot convert value of type 'NSEvent.ModifierFlags' to expected argument type 'UInt8'

Replacing event.ModifierFlags with UInt8(event.modifierFlags.rawValue) etc also fails.

How do I fix this?

Edit:

Directly comparing event.modifierFlags == keymask fails (Even when I press only option-tab (and no other modifier key)).

On printing event.modifierFlags to console, a different value gets printed depending on whether I press the left or right option keys.

print (event.modifierFlags) // prints: ModifierFlags(rawValue: 524576) using LEFT OPTION 
// and  ModifierFlags(rawValue: 524608) when using RIGHT OPTION.

print(keymask) // prints: ModifierFlags(rawValue: 524288)

At this point my vague hunch is that I need to ignore the lower order bits and compare only the higher order ones. I just don't know how to go about doing this.

Answer 1

NSEvent.ModifierFlags is an OptionSet (which is a SetAlgebra). See the documentation for those as needed.

Given your current code, you basically want to see if the only flags set are those in the mask. But you do need to mask out for just the device independent flags.

Update your if as:

if event.keyCode == keyCode && event.modifierFlags.intersection(.deviceIndependentFlagsMask) == keymask {
}