How to manage multiple NSWindows in a dictionary - swift

Question

What I'm trying to do:
I'm currently developing a Command-Line-Tool that creates a blurred window for each desktop space available. I save these windows in a dictionary where the spaceIdentifier is the keyand the NSWindow is the value.
In order to keep the windows in sync with the spaces I periodically check if there are new spaces or if spaces are closed.
My Code:
import AppKit
import Foundation
func createBlurWindow(screen: NSScreen?, contentRect: NSRect, brightness: Int) -> NSWindow
{
# irrelevant code that creates a blurred window
}
class AppController: NSObject, NSApplicationDelegate
{
var spaceWindowList: [NSNumber: NSWindow] = [:]
func applicationDidFinishLaunching(_ aNotification: Notification)
{
self.manageWindows()
Timer.scheduledTimer(timeInterval: 5.0, target: self, selector: #selector(self.manageWindows), userInfo: nil, repeats: true)
}
#objc func manageWindows()
{
// create windows
for scr in NSScreen.screens {
let scrHeight = scr.frame.height
let scrWidth = scr.frame.width
let windowHeight = CGFloat(22)
let size = CGRect(x: 0, y: scrHeight-windowHeight, width: scrWidth, height: windowHeight)
let currentScreenSpaces = WindowHelper.getSpacesforScreen(scr)
for space in currentScreenSpaces!
{
if self.spaceWindowList[space] == nil
{
let w = createBlurWindow(screen: scr, contentRect: size, brightness: 9)
let windowID = NSNumber.init(value: w.windowNumber)
// #TODO this may fail if the space was created just now -> fix this by waiting some time
WindowHelper.moveWindow(windowID, toSpace: space)
self.spaceWindowList[space] = w
// debuginfo
let displayNr = scr.deviceDescription[NSDeviceDescriptionKey("NSScreenNumber")]!
print(getTime(), " Display:", displayNr, " added Window(", windowID , ") for Space: ", space, separator: "")
}
}
}
let currentSpaces = WindowHelper.getAllSpaces()
for (space, window) in self.spaceWindowList
{
// destroy window if space was closed
if !(currentSpaces?.contains(space))!
{
window.close()
//self.spaceWindowList.removeValue(forKey: space)
// debuginfo
print(getTime(), "Destroyed window of closed Space:", space)
}
}
}
}
let app = NSApplication.shared
let controller = AppController()
app.delegate = controller
app.run()
The complete source can be found here
My Problem:
When detecting that a space was closed I try to programatically close the corresponding NSWindow, however the next time manageWindows() is called the application segfaults on this loop: for (space, window) in self.spaceWindowList. To debug I activated zombieobjects and got the following errormessage -[NSWindow retain]: message sent to deallocated instance 0x101241150
I don't understand why there is still a pointer to my window the next time spaceWindowList is iterated. I also tried to nil the dictionary entry with self.spaceWindowList.removeValue(forKey: space) but that also lead to a segfault.
I'm fairly new to swift and macdev in general so I'm not that confident with memory management in swift.
I would really appreciate if someone could tell me the best way to safely close windows organized in some kind of dictionary/map/whatever.
PS:
If you are wondering why I don't use .canJoinAllSpaces instead of creating the window for each space: When using .canJoinAllSpaces you can see the blurred NSEffectView flickering on a space change if the spaces have different desktop images. The only way to circumvent this is to create individual windows for each space.