To update complications on the watch, I use a singleton class ComplicationController (irrelevant code has been omitted below):
final class ComplicationController: NSObject, CLKComplicationDataSource {
static let shared = ComplicationController() // Instantiate the singleton
private override init() {
super.init()
print("====self: \(self): init")
} // Others can't init the singleton
}
The singleton is created on the watch by the extension delegate:
class ExtensionDelegate: NSObject, WKExtensionDelegate {
override init() {
super.init()
_ = ComplicationController.shared
}
}
When I launch the watch extension with a breakpoint at the print statement above, the execution breaks and the stack trace is:
When I then execute the print statement in a single step, the debugger shows:
====self: <Watch_Extension.ComplicationController: 0x7bf35f20>: init
When I then continue, the execution breaks again at the same breakpoint, and the stack trace is:
After another single step, the debugger shows:
====self: <Watch_Extension.ComplicationController: 0x7d3211d0>: init
Obviously, the CLKComplicationServer has created another instance of the singleton.
My question is: Did I something wrong or is this a bug? If it is a bug, is there a workaround?
PS: It does not help not to initialize ComplicationController in the ExtensionDelegate. In this case, the 2nd instance is created as soon as ComplicationController.shared is used anywhere in the code.
I found a workaround:
Do not instantiate the singleton in the app, i.e. do not use ComplicationController.shared anywhere.
If you have to call functions in ComplicationController.shared, send a notification, e.g. to the default notification center.
The ComplicationController singleton had to have registered for such notifications, and when it receives one, it has to execute the required function.
This did work for me.
Related
I have the following code:
class Problem{
init(){
print("Problem init");
}
deinit{
print("Problem deinit");
}
}
var list = Problem();
The output:
Problem init
The following causes the program to call deinit:
class Problem{
init(){
print("Problem init");
}
deinit{
print("Problem deinit");
}
}
do {
var list = Problem();
}
Questions:
Why isn't deinit called the first time?
Is there a way to guarantee that deinit will always be called for Problem in code that I have not control of how it is written(i.e., user code)?
P.S. I know there is most likely an obvious reason that I, as a programmer that is new to Swift, have overlooked.
It is because of the difference in Scopes between these two example that you create by adding the do-block.
In the first scenario, when that code is ran, an instance of Problem is created (initialized) at a Global Scope (outside of a class or struct definition in Swift) and then it just sits there. The program does not end and it is never de-initialized.
In the second scenario, you create the instance of Problem inside a the do-block, so it's scope is limited to inside that block. When the do-block ends, the instance is dereferenced, and thus de-initialized.
Setup:
I have a ViewController ProblemView and class A. I pass ProblemView to class A, so I can work on it. It looks like this (simplified):
class ProblemView: UIViewController{
var instanceOfA = A()
instanceOfA.passView(passedVC: self)
}
class A{
var workOn = ProblemView()
func passView(passedVC: ProblemView){
workOn = passedVC
// I noticed, if I declare a varible locally like var workOn2 = passedVC, my problem is solved -
// but I need the variable globally, because I don't want to pass it around within this class
}
func doSth(){
// here I interact with variables of the passed ViewController
}
}
Problem: Whenever I restart this process within the app the memory increases every single time until I get memory error.
What I tried: I added deinit to both classes. class A is always deinitialized but class ProblemView is not (this might be the problem?).
I also found out, that when I don't declare workOn globally but within the passView function, then it works just fine. But I need have the variable globally, because I use it within many different functions of A. What could be a solution or workaround to this problem?
Strong references to each other.
Try to change class A:
weak var workOn: ProblemView?
func passView(passedVC: ProblemView){
workOn = passedVC
// I noticed, if I declare a varible locally like var workOn2 = passedVC, my problem is solved -
// but I need the variable globally, because I don't want to pass it around within this class
}
func doSth(){
// here I interact with variables of the passed ViewController
}
I have a NSViewController that has a class variable as follows:
class ServerAdminViewController: NSViewController, NSTextFieldDelegate, MyTableViewDelegate {
var myClass = MyClass()
func showAdmin(window: NSWindow, myClass: MyClass) {
self.myClass = myClass
window.makeKeyAndOrderFront(self)
NSApp.activate(ignoringOtherApps: true)
}
An instance of this class is instantiated in the App initialization. Later when user clicks on a menu item, I want to show a window and use that value as a singleton for the app, during the time this window is open, also being able to modify myClass. However, the line where the instance variable is declared is being executed multiple times and after the self.myClass = myClassassignment, resetting the object (this is a menubar app that opens a window).
Tried
Several things, ex. removing the parameterless constructor from myClass, declaring that variable private and with a "!", adding init methods to the ViewController (without success) and some other failed attempts.
Question
How to make myClass a singleton and share it accross the application (i.e. make it available to this window) without reinitializing it?
Soo there use to be a bunch of stuff to do this with dispatchOnce and things like that. But now the way I do this is by declaring a shared static variable on my class. This will not handle persistence but it will solve your problem creating your class many times. The shared reference with only be recreated on use after being released. Or if it has never been used before. The class variable is also handy for retrieving the class for many controllers.
class MyClass {
static let shared = MyClass()
}
class MyViewController: UIViewController {
let myClass = MyClass.shared
}
I’ve created a Swift macOS app which uses SMJobBless to create a helper with escalated privileges. This works fine—the helper gets installed to /Library/Privileged Helper Tools and an accompanying LaunchDaemon gets created in /Library/LaunchDaemons. However, the helper is unable to start successfully. Instead, it crashes with an “Illegal instruction: 4” message.
I’ve prepared the helper to respond to XML connections by implementing the NSXPCListenerDelegate protocol. Here‘s my Helper main.swift code:
import Foundation
class HelperDelegate: NSObject, NSXPCListenerDelegate {
func listener(_ listener: NSXPCListener, shouldAcceptNewConnection newConnection: NSXPCConnection) -> Bool {
newConnection.exportedInterface = NSXPCInterface(with: HelperToolProtocol.self)
newConnection.exportedObject = HelperTool()
newConnection.resume()
return true
}
}
let delegate = HelperDelegate()
let listener = NSXPCListener.service()
listener.delegate = delegate
listener.resume()
The crash occurs on the last line, listener.resume().
I tried to launch the helper app manually from the command line (which is identical to what the LaunchDaemon does) and, again, it crashes with the above error message printed to stdout. I don’t have any more ideas on how to test this for the root cause. My implementation is more than rudimentary, following Apple’s guidlines for implementing XM services. Also, the various posts on SO regarding XML services haven’t helped me in resolving this issue. Has anyone of you tried to create a privileged helper in Swift successfully? BTW, the app is not sandboxed.
For the sake of completeness, here’s the code for the HelperTool class referenced in my HelperDelegate class above:
import Foundation
class HelperTool: NSObject, HelperToolProtocol {
func getVersion(withReply reply: (NSData?) -> ()) {
let version = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString" as String) as? String ?? "<unknown version>"
let build = Bundle.main.object(forInfoDictionaryKey: kCFBundleVersionKey as String) as? String ?? "<unknown build>"
if let d = "v\(version) (\(build))".data(using: .utf8, allowLossyConversion: false) {
reply(d as NSData)
}
}
}
And finally the HelperToolProtocol:
import Foundation
#objc(HelperToolProtocol) protocol HelperToolProtocol {
func getVersion(withReply: (NSData?) -> ())
}
Thanks for any help!
After days of testing I finally found a solution which makes my XPC helper launch correctly and respond to any messages. The problem lies in the last three lines of the main.swift module which currently read
let listener = NSXPCListener.service()
listener.delegate = delegate
listener.resume()
which, as put in the question, make the helper crash immediately upon the very last line.
I took these lines directly from Apple’s Creating XPC Services documentation. Here’s the documentation for the NSXPCListener resume() function:
If called on the service() object, this method never returns. Therefore, you should call it as the last step inside the XPC service's main function after setting up any desired initial state and configuring the listener itself.
The solution is to not call the NSXPCListener.service() singleton object but rather instantiate a new NSXPCListener object using the init(machServiceName:)initializer passing the same Mach service name that is being used on the main app’s XPC connection. As resume() in this case would resume immediately—thus terminating the helper—you have to put it on the current run loop to have it run indeterminately. Here’s the new, working code:
let listener = NSXPCListener(machServiceName: "Privilege-Escalation-Sample.Helper")
listener.delegate = delegate
listener.resume()
RunLoop.current.run()
This sounds like a stupid question, but I have been trying to find a solution for hours now, and I still don't know what to do. I am using Swift 3.0, and I am having an issue calling a method inside a singleton class from a selector inside another class. My singleton class is as follows:
class Singleton : NSObject {
static let sharedInstance = Singleton()
private override init() {} // defeats instantiation
func myAction() {
// do something useful...
}
}
Then, here is the class from which I am calling the method contained in the Singleton:
class StatusBarPresenter {
func addItemsToMenu(menu: NSMenu) {
...
menu.insertItem(withTitle: "Disconnect this network",
action: #selector(Singleton.sharedInstance.myAction),
keyEquivalent: "D", at: 4)
...
}
}
Xcode doesn't complain about the code... it compiles without any errors or warnings, but the selector doesn't work. The UIMenuItem that I add to the menu is disabled, which means that the selector is not working. If the selector instead calls a method inside the class, everything works fine just as usual. This is a screenshot of what I am getting:
Thanks to Martin R. for pointing out that in my code I was not setting an explicit target for the UIMenuItem, leading to it being nil and ultimately self.
The following line added to the addItemsToMenu function after the call to insertItem solves the problem:
menu.item(at: 4)?.target = Singleton.sharedInstance