Programatically changing button text and actions when a modifier key is pressed - swift

Question

I would like to change the text of an NSButton when the ⌥ Option key is pressed - similar to the copy dialog when colliding files are detected on OS X which changes "Keep Both" to "Merge" when the option key is held.
In my case, I would like to change a button with text, say, "delete" to "quit" when I hold the option key. Additionally, its functionality should change in accordance with its title, much like the options in the Copy dialog.
Can this be done programatically in Swift?

Answer 1

You can subscribe using addLocalMonitorForEvents(matching:) and detect if option key pressed like this:
var optionKeyEventMonitor: Any? // property to store reference to the event monitor
// Add the event monitor
optionKeyEventMonitor = NSEvent.addLocalMonitorForEvents(matching: .flagsChanged) { event in
if event.modifierFlags.contains(.option) {
self.button.title = "copy"
self.button.action = #selector(self.copyButtonClicked(_:))
} else {
self.button.title = "delete"
self.button.action = #selector(self.deleteButtonClicked(_:))
}
return event
}
#IBAction func copyButtonClicked(_ sender: Any) {
Swift.print("Copy button was clicked!")
}
#IBAction func deleteButtonClicked(_ sender: Any) {
Swift.print("Delete button was clicked!")
}
Remember to remove the event monitor when you are done:
deinit {
if let eventMonitor = optionKeyEventMonitor {
NSEvent.removeMonitor(eventMonitor)
}
}
If you don't want a separate method called depending on the option key state, you can check modifierFlags when button is clicked instead:
#IBAction func buttonClicked(sender: NSButton) {
if NSEvent.modifierFlags().contains(.option) {
print("option pressed")
} else {
print("option not pressed")
}
}

Answer 2

In Swift 3 code:
func optionKeyDown() -> Bool
{
return NSEvent.modifierFlags().contains(NSEventModifierFlags.option)
}
if optionKeyDown()
{
print ("do option code")
}
else
{
print ("do normal code")
}