NSView that closes itself when clicking outside

ModalView.swift

//  MIT License - © 2017 Jonathan Cole.

import Cocoa

/**
 A view with the ability to hide itself if the user clicks outside of it.
 */
class ModalView: NSView {
    private var monitor: Any?
    
    deinit {
        // Clean up click recognizer
        removeCloseOnOutsideClick()
    }
    
    /**
     Creates a monitor for outside clicks. If clicking outside of this view or
     any views in `ignoringViews`, the view will be hidden.
     */
    func addCloseOnOutsideClick(ignoring ignoringViews: [NSView]? = nil) {
        monitor = NSEvent.addLocalMonitorForEvents(matching: NSEventMask.leftMouseDown) { (event) -> NSEvent? in
            if !self.frame.contains(event.locationInWindow) && self.isHidden == false {
                
                // If the click is in any of the specified views to ignore, don't hide
                for ignoreView in ignoringViews ?? [NSView]() {
                    let frameInWindow: NSRect = ignoreView.convert(ignoreView.bounds, to: nil)
                    if frameInWindow.contains(event.locationInWindow) {
                        // Abort if clicking in an ignored view
                        return event
                    }
                }
                
                // Getting here means the click should hide the view
                // Perform your hiding code here
                self.isHidden = true
            }
            return event
        }
    }
    
    
    func removeCloseOnOutsideClick() {
        if monitor != nil {
            NSEvent.removeMonitor(monitor!)
            monitor = nil
        }
    }
    
}