Making copy & paste work with NSTextField

When I started working on my open-source Localization Editor, which is a macOS application, I encountered some things that were a bit strange compared to iOS development. One of those things is that copy & paste does not automatically work on a NSTextField.

To be exact, copy & paste works on a NSTextField as long as you do not delete the Edit menu from the standard Main menu. If you do that for some reason, you have to implement all the copy & paste functionality yourself.

The key to the implementation is overriding the performKeyEquivalent method and manually checking for cmd + c/v/x/z/a

final class EditableNSTextField: NSTextField {

    private let commandKey = NSEvent.ModifierFlags.command.rawValue
    private let commandShiftKey = NSEvent.ModifierFlags.command.rawValue | NSEvent.ModifierFlags.shift.rawValue

    override func performKeyEquivalent(with event: NSEvent) -> Bool {
        if event.type == NSEvent.EventType.keyDown {
            if (event.modifierFlags.rawValue & NSEvent.ModifierFlags.deviceIndependentFlagsMask.rawValue) == commandKey {
                switch event.charactersIgnoringModifiers! {
                case "x":
                    if NSApp.sendAction(#selector(NSText.cut(_:)), to: nil, from: self) { return true }
                case "c":
                    if NSApp.sendAction(#selector(NSText.copy(_:)), to: nil, from: self) { return true }
                case "v":
                    if NSApp.sendAction(#selector(NSText.paste(_:)), to: nil, from: self) { return true }
                case "z":
                    if NSApp.sendAction(Selector(("undo:")), to: nil, from: self) { return true }
                case "a":
                    if NSApp.sendAction(#selector(NSResponder.selectAll(_:)), to: nil, from: self) { return true }
                default:
                    break
                }
            } else if (event.modifierFlags.rawValue & NSEvent.ModifierFlags.deviceIndependentFlagsMask.rawValue) == commandShiftKey {
                if event.charactersIgnoringModifiers == "Z" {
                    if NSApp.sendAction(Selector(("redo:")), to: nil, from: self) { return true }
                }
            }
        }
        return super.performKeyEquivalent(with: event)
    }
}
macOS  Swift 

See also