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
        }
    }
    
}

Sample usage:

(Presume some instance of ModalView called modal exists already)

modal.addCloseOnOutsideClick()

Now modal will hide itself if the user clicks outside of it.

If you don't want the modal to close when clicking certain views (for example, a button that opens the view):

modal.addCloseOnOutsideClick(ignoring: [someView, someOtherView])