// magic functions to get the CoreData context and entity's instance
let context = getContext()
let entity = getEntity()

// nil out the binary blob, so CoreData erases the file in _EXTERNAL_DATA
entity.setValue(nil, forKey: "image")
context.save()

// then actually save your new blob
entity.setValue(blob, forKey: "image")
context.save()

class GNLOutlineView: NSOutlineView {
  override func makeView(withIdentifier identifier: NSUserInterfaceItemIdentifier, owner: Any?) -> NSView? {

    // intercept disclosure button creation
    if identifier == NSOutlineView.disclosureButtonIdentifier {
      // then create our custom button
      let myView = super.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "MyDisclosureButton"), owner: owner) as! NSButton
      
      // we need to change the identifier so that the outline view knows to use this view as the disclosure button
      myView.identifier = identifier      
      return myView
    }

    // for everything else, use the default function
    return super.makeView(withIdentifier: identifier, owner: owner)
  }
}

// get the original disclosure button
let originalButton = super.makeView(withIdentifier: identifier, owner: owner) as! NSButton

myView.target = originalButton.target
myView.action = originalButton.action

open func applicationWillFinishLaunching(_ notification: Notification) {
    initializeURIOptions()
}

fileprivate func initializeURIOptions() {
    // register to listen to the url event
    let appleEventManager = NSAppleEventManager.shared()
    appleEventManager.setEventHandler(self, andSelector: #selector(handleGetURLEvent(event:withReplyEvent:)), forEventClass: AEEventClass(kInternetEventClass), andEventID: AEEventID(kAEGetURL))
}

@objc fileprivate func handleGetURLEvent(event: NSAppleEventDescriptor?, withReplyEvent replyEvent: NSAppleEventDescriptor?) {
    guard let event = event else {
        return
    }
    // our URL event is in this format:
    // myapp://param1=val1&param2=val2&paramN=valN
    
    // grab the query pairs, that is the pairs separated by '&'
    guard let paramDesc = event.paramDescriptor(forKeyword: AEKeyword(keyDirectObject))?.stringValue,
        let url = NSURL(string: paramDesc),
        let queryPairs = url.query?.components(separatedBy: "&") else {
            return
    }
    
    // parse the key/value pair
    // querypairs is assumed to be in the form of "key=value"
    var settingPairs = [String: String]()
    for query in queryPairs {
        let kvp = query.components(separatedBy: "=")
        if kvp.count != 2 {
            continue
        }
        
        let key = kvp[0].lowercased()
        let value = kvp[1].lowercased()
        settingPairs[key] = value
    }
    
    // do stuff with settingPairs
}

internal var selectedIndex: AnyObject! {
    didSet {
        let oldIndex = oldValue as? Int
        let newIndex = selectedIndex as? Int
        print("selectedIndex didSet, old: \(oldIndex), new: \(newIndex)")
    }
}

popUpButton.selectItem(at: 2)

// App 1
if let defaults = UserDefaults(suiteName: "com.gietal.sandbox.group") {
    defaults.set(123, forKey: "myKey")
}

// App 2
if let defaults = UserDefaults(suiteName: "com.gietal.sandbox.group") {
    let value = defaults.value(forKey: "myKey")
    print("value: \(value)")
}