UI: use NotificationToken to properly clean up observers

When the variable goes out of scope, the observer isn't removed unless
an explicit call is made to the token.

Signed-off-by: Andrej Mihajlov <and@mullvad.net>

Sources/Shared/NotificationToken.swift

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: MIT
+// Copyright © 2018-2020 WireGuard LLC. All Rights Reserved.
+
+import Foundation
+
+/// This source file contains bits of code from:
+/// https://oleb.net/blog/2018/01/notificationcenter-removeobserver/
+
+/// Wraps the observer token received from
+/// `NotificationCenter.addObserver(forName:object:queue:using:)`
+/// and unregisters it in deinit.
+final class NotificationToken {
+    let notificationCenter: NotificationCenter
+    let token: Any
+
+    init(notificationCenter: NotificationCenter = .default, token: Any) {
+        self.notificationCenter = notificationCenter
+        self.token = token
+    }
+
+    deinit {
+        notificationCenter.removeObserver(token)
+    }
+}
+
+extension NotificationCenter {
+    /// Convenience wrapper for addObserver(forName:object:queue:using:)
+    /// that returns our custom `NotificationToken`.
+    func observe(name: NSNotification.Name?, object obj: Any?, queue: OperationQueue?, using block: @escaping (Notification) -> Void) -> NotificationToken {
+        let token = addObserver(forName: name, object: obj, queue: queue, using: block)
+        return NotificationToken(notificationCenter: self, token: token)
+    }
+}

Sources/WireGuardApp/Tunnel/TunnelsManager.swift

@@ -23,9 +23,9 @@ class TunnelsManager {
     private var tunnels: [TunnelContainer]
     weak var tunnelsListDelegate: TunnelsManagerListDelegate?
     weak var activationDelegate: TunnelsManagerActivationDelegate?
-    private var statusObservationToken: AnyObject?
-    private var waiteeObservationToken: AnyObject?
-    private var configurationsObservationToken: AnyObject?
+    private var statusObservationToken: NotificationToken?
+    private var waiteeObservationToken: NSKeyValueObservation?
+    private var configurationsObservationToken: NotificationToken?
 
     init(tunnelProviders: [NETunnelProviderManager]) {
         tunnels = tunnelProviders.map { TunnelContainer(tunnel: $0) }.sorted { TunnelsManager.tunnelNameIsLessThan($0.name, $1.name) }
@@ -406,7 +406,7 @@ class TunnelsManager {
     }
 
     private func startObservingTunnelStatuses() {
-        statusObservationToken = NotificationCenter.default.addObserver(forName: .NEVPNStatusDidChange, object: nil, queue: OperationQueue.main) { [weak self] statusChangeNotification in
+        statusObservationToken = NotificationCenter.default.observe(name: .NEVPNStatusDidChange, object: nil, queue: OperationQueue.main) { [weak self] statusChangeNotification in
             guard let self = self,
                 let session = statusChangeNotification.object as? NETunnelProviderSession,
                 let tunnelProvider = session.manager as? NETunnelProviderManager,
@@ -438,7 +438,7 @@ class TunnelsManager {
     }
 
     func startObservingTunnelConfigurations() {
-        configurationsObservationToken = NotificationCenter.default.addObserver(forName: .NEVPNConfigurationChange, object: nil, queue: OperationQueue.main) { [weak self] _ in
+        configurationsObservationToken = NotificationCenter.default.observe(name: .NEVPNConfigurationChange, object: nil, queue: OperationQueue.main) { [weak self] _ in
             DispatchQueue.main.async { [weak self] in
                 // We schedule reload() in a subsequent runloop to ensure that the completion handler of loadAllFromPreferences
                 // (reload() calls loadAllFromPreferences) is called after the completion handler of the saveToPreferences or

Sources/WireGuardApp/UI/macOS/ViewController/LogViewController.swift

@@ -18,6 +18,9 @@ class LogViewController: NSViewController {
         }
     }
 
+    private var boundsChangedNotificationToken: NotificationToken?
+    private var frameChangedNotificationToken: NotificationToken?
+
     let scrollView: NSScrollView = {
         let scrollView = NSScrollView()
         scrollView.hasVerticalScroller = true
@@ -104,13 +107,13 @@ class LogViewController: NSViewController {
         clipView.documentView = tableView
         scrollView.contentView = clipView
 
-        _ = NotificationCenter.default.addObserver(forName: NSView.boundsDidChangeNotification, object: clipView, queue: OperationQueue.main) { [weak self] _ in
+        boundsChangedNotificationToken = NotificationCenter.default.observe(name: NSView.boundsDidChangeNotification, object: clipView, queue: OperationQueue.main) { [weak self] _ in
             guard let self = self else { return }
             let lastVisibleRowIndex = self.tableView.row(at: NSPoint(x: 0, y: self.scrollView.contentView.documentVisibleRect.maxY - 1))
             self.isInScrolledToEndMode = lastVisibleRowIndex < 0 || lastVisibleRowIndex == self.logEntries.count - 1
         }
 
-        _ = NotificationCenter.default.addObserver(forName: NSView.frameDidChangeNotification, object: tableView, queue: OperationQueue.main) { [weak self] _ in
+        frameChangedNotificationToken = NotificationCenter.default.observe(name: NSView.frameDidChangeNotification, object: tableView, queue: OperationQueue.main) { [weak self] _ in
             guard let self = self else { return }
             if self.isInScrolledToEndMode {
                 DispatchQueue.main.async {