Debug responder chain in Cocoa

CustomWindow.swift

class CustomWindow: NSWindow {
    override init(contentRect: NSRect, styleMask style: NSWindow.StyleMask, backing backingStoreType: NSWindow.BackingStoreType, defer flag: Bool) {
        super.init(contentRect: contentRect, styleMask: style, backing: backingStoreType, defer: flag)
    }

    override func makeFirstResponder(_ responder: NSResponder?) -> Bool {
        self.printResponderChain(responder)
        return super.makeFirstResponder(responder)
    }

    func printResponderChain(_ responder: NSResponder?) {
        guard let responder = responder else { return; }

        Swift.print(responder)
        printResponderChain(responder.nextResponder)
    }

    override func sendEvent(_ event: NSEvent) {
        super.sendEvent(event)
    }
}