In my application, I uses NSRunAlertPanel to confirm the quit by the user.
When I run my application under instruments to detect memory leaks, it shows memory leak in the following code.
-(void)CloseWithConfirm
{
int answer;
//Here, it is showing memory leak.
answer = NSRunAlertPanel (#"Quit Confirmation", #"Do you want to quit?", #"Yes", #"No", #"Cancel");
if(NSAlertDefaultReturn == answer)
[self close];
}
Any clue on it?
The NSRunAlertPanel is actually calling runModalForWindow: and creating a modal event loop. Even though hitting the confirmation button on the modal window dismisses the window, it doesn't destruct the modal loop that was created. In your return if statement try doing this:
if (NSAlertDefaultReturn == answer) {
[NSApp stopModal];
[self close];
}
See if the memory leak stops with this code.
FWIW, since you are closing down the app when this method exits, having a memory leak right at the end probably isn't affecting things too much.
Related
I have a relatively-lengthy task. So I bring up a separate window (NSWindowController) from AppDelegate to show progress. It goes like
//AppDelegate.m
if (self.progresswindow == nil) {
self.progresswindow = [[ProgressController alloc] initWithWindowNibName:#"ProgressController"];
}
[progresswindow showWindow:self];
//[[progresswindow window] setReleasedWhenClosed:NO];
[NSApp runModalForWindow:progresswindow.window];
When a task is complete, the progress window will close itself.
//ProgressController.m
[NSApp stopModal];
[self close];
It works fine. But when I click on a button to start another session of a task with the same window, the application won't run a task although it opens. It appears that the last instance hasn't be released. The progress window has the following lines.
- (void)windowDidLoad {
NSLog(#"Hey!");
}
And NSLog won't be called for the 2nd time. I wonder what I'm doing wrong? Calling setReleasedWhenClosed from AppDelegate has no effect. I have the Release When Closed checkbox enabled, anyway. I read something like I need to observe NSWindowWillCloseNotification the progress window in a different topic so that I can release it when it closes. But I'm using ARC. So I can't manually release it, can I? Meanwhile, if I open Apple's sample (TableViewPlayground), it seems that they use this notification. Furthermore, I've read this topic and this topic. But I don't know what the problem is.
I appreciate any advice. Thank you for your time.
Release the Progress-Window-Controller.
In my document-based application, I have overridden the method openDocument: in my subclass of NSDocumentcontroller so that I can display my own openPanel. I pass the chosen URLs to the method openDocumentWithContentsOfURL:display:completionHandler:. I use this code for the call:
[self openDocumentWithContentsOfURL:[chosenFiles objectAtIndex:i] display:YES completionHandler:^(NSDocument *document, BOOL documentWasAlreadyOpen, NSError *error) {
if (document == nil)
{
NSAlert* alert = [NSAlert alertWithError:error];
[alert runModal];
}
}];
So I want to display the passed error if nil gets returned as a reference to the document. The problem is, that the program just "freezes" after I press the "Open" button in the open panel. Then I need to manually stop the program with the "stop" button in Xcode. No spinning beach ball appears, though. If I comment the line "[alert runModal]", the program does not freeze any more, but no alert is displayed, of course.
Now the strange thing: The code works sometimes. If I switch from Xcode to my browser and back and I run the program again, it sometimes works flawlessly and the error is displayed. After some time it stops working again. It is unpredictable, but most of the time it doesn't work.
All this sounds like a race-condition to me. It certainly has something to do with the block? But what do I do wrong?
Converting my comment to an answer:
runModel on the main thread.
[alert performSelectorOnMainThread:#selector(runModal) withObject:nil waitUntilDone:NO];
I think runModel needs to be called on the main thread because it's part of the AppKit framework, and it's estentially triggering UI graphics. I believe all calls to the AppKit framework or to any method that manipulates graphics needs to be on the main thread.
Ok, here is the deal, I hate putting out questions about my debugging and crashes. Because I usually handle them myself, but I just cannot get my way around this, even after viewing multiple questions already.
Ok so here is the problem, I find my app randomly on and off crashing with this stack trace:
*** -[ViewController respondsToSelector:]: message sent to deallocated instance 0x1e5d2ef0
Where ViewController can vary, sometimes the place where my code crashes, has NO relevance to that particular ViewController and doesn't own or call it.
Also, to get that console trace, I have enabled Zombies, otherwise I would get no console print at all, I would only get: objc_msgSend, which I know means I am messaging something that is released. But I cannot find where that is... I am really stuck! Usually I always debug my crashes, so I am really stuck on this.
Again, this crashes in different places at different times, on and off. And the place it crashes has almost no relevance to the ViewController. And I find this very confusing.
Do you need any of my code? I have a lot of files and since it is crashing in different places, distributing my code will be a mess!
I have tried to add symbolic breakpoints with no luck, and Zombies is not available on the Instruments application for iOS. I cannot run my app on the simulator as it has unsupportive architecture frameworks for it.
Thanks everyone...
Use Instruments to track down deallocated instance errors. Profile your application (Cmd ⌘+I) and choose Zombies template. After your application is running, try to crash it. You should get something like that:
Click on the arrow next to address in the popover to show object that was called after it was deallocated.
You should see now every call that has changed retain count of this object. This could be because sending directly retain/release messages as well as draining autorelease pools or inserting into NSArrays.
RefCt column shows retainCount after action was invoked and Responsible Caller shows class name and method in which it was performed. When you double click on any retain/release, instruments will show you line of code where this was performed (If this isn't working, you can examine call by selecting it and choosing its counterpart in Extended Detail pane):
This will let you examine all the retainCount lifecycle of object and probably you'll find your problem right away. All you got to do is find missing retain for latest release.
had a similar problem. In my case a viewController needed to get navigationController events, so it was registering as the navigation controller delegate:
self.navigationController.delegate = self;
The crash occurs when that controller was dealloc'ed but was still the delegate for the view controller. Adding this code in dealloc had no effect:
-(void) dealloc
{
if (self.navigationController.delegate == self)
{
self.navigationController.delegate = nil;
}
because at the point that dealloc is called, the view controller has already been removed from the view hierarchy, so self.navigationController is nil, so the comparison is guaranteed to fail! :-(
The solution was to add this code to detect the VC leaving the view hierarchy just before it actually does so. It uses a method introduced in iOS 5 to determine when the view is being pop'ed and not pushed
-(void) viewWillDisappear:(BOOL) animated
{
[super viewWillDisappear:animated];
if ([self isMovingFromParentViewController])
{
if (self.navigationController.delegate == self)
{
self.navigationController.delegate = nil;
}
}
}
No more crashes!
For anyone who can't solve it, here are some other techniques:
https://stackoverflow.com/a/12264647/539149
https://stackoverflow.com/a/5698635/539149
https://stackoverflow.com/a/9359792/539149
https://stackoverflow.com/a/15270549/539149
https://stackoverflow.com/a/12098735/539149
You can run Instruments in Xcode 5 by clicking the project popup->Edit Scheme...Profile ->Instrument and choose Allocations or Leaks, then profile your app, then stop Instruments, click the info button in Allocations and "Enable NSZombie Detection".
However, for the messages that come directly from the com.apple.main-thread, this probably won't reveal anything.
I banged my head on this for over two hours and the answer turned out to be an over-release, which I discovered by commenting out a copy of my project by brute force until I found the culprit:
[viewController release];
viewController = NULL;
The problem is that release doesn't set the variable to NULL.
That means that setting it to NULL calls release again, decrementing the refcount and freeing the memory immediately until later when the variables that reference viewController are finished with it.
So either enable ARC or make sure your project consistently uses release or NULL but not both. My preference is to use NULL because then there is no chance of referencing a zombie but it makes finding where objects are released more difficult.
I had met the same problem in iOS yesterday. I have made IAP in App "About" subview, and I have added Transaction Observer in "About" viewDidLoad. When I purchase for the first time, no problem, but after I back to main window and enter about subview to purchase again, the problem "message sent to deallocated instance" happened, and the App crashed.
- (void)viewDidLoad
{
[[SKPaymentQueue defaultQueue] addTransactionObserver:self]; object:nil];
}
After I remove Transaction Observer in dealloc, the problem is solved.
- (void)dealloc
{
// Even though we are using ARC, we still need to manually stop observing any
// NSNotificationCenter notifications. Otherwise we could get "zombie" crashes when
// NSNotificationCenter tries to notify us after our -dealloc finished.
[[SKPaymentQueue defaultQueue] removeTransactionObserver:self];
}
I had a very similar issue and I figured out it was due to navigation controller delegates set.
The below solved my issue,
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
if (self.navigationController.delegate != self) {
self.navigationController.delegate = self;
}
}
-(void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
if (self.navigationController.delegate == self) {
self.navigationController.delegate = nil;
}
}
Had the same problem in OS X.
To solve this not enough - (void)dealloc method as #SoftwareEvolved already said. But unfortunately - (void)viewWillDisappear is available only on version 10.10 and later.
I introduced custom method in my NSViewController subclass where set all the zombie-dangerous references to nil. In my case that was NSTableView properties (delegate and dataSource).
- (void)shutdown
{
self.tableView.delegate = nil;
self.tableView.dataSource = nil;
}
That's all. Each time I'm about to remove view from the superview need call this method.
I had the same Problem.It was difficult to find which delegate cause issue, because it does not indicate any line or code statement So I have try some way, Maybe it becomes helpful to you.
Open xib file and from file's owner, Select "show the connections inspector" right hand side menu. Delegates are listed, set them to nil which are suspected.
(Same as my case)Property Object like Textfield can create issue, So set its delegates to nil.
-(void) viewWillDisappear:(BOOL) animated{
[super viewWillDisappear:animated];
if ([self isMovingFromParentViewController]){
self.countryTextField.delegate = nil;
self.stateTextField.delegate = nil;
}
}
When I'm done with a popup NSWindow, I invoke the following lines of code:
if (imageDroppedActionPopup) {
[[self window] removeChildWindow:imageDroppedActionPopup];
[imageDroppedActionPopup orderOut:nil];
[imageDroppedActionPopup close];
imageDroppedActionPopup = nil;
}
I'm now wondering if I can replace
[imageDroppedActionPopup close];
with
[imageDroppedActionPopup release];
It seems to work correctly. But I was wondering if it is correct.
The reason I'm doing this, is that if I use close for some reason the app focus come back to the main document window, and not the current NSWindowController window, which is the above mentioned popup parent.
close removes the window from screen, release decreases object's retain counter and may or may not cause it to be deallocated.
It seems to work because being deallocated implies being removed from screen, but these methods can never replace one another. Even if you are the only owner you can never be sure that release will cause immediate deallocation (and therefore nor immediate disappearance of the window), because the window might be temporary retained by someone else.
When you need the window to close, call close. And you must only call release on objects which you have retained, allocated or copied, strictly according to memory management rules.
Considering that replacing close with release did not cause crash, I think you need both.
You don't need to use close. Calling orderOut: will close the window. You should do this before removing it as a child window. This will prevent the window ordering problems that you're seeing.
Just do this:
if (imageDroppedActionPopup)
{
[imageDroppedActionPopup orderOut:nil];
[[self window] removeChildWindow:imageDroppedActionPopup];
[imageDroppedActionPopup release];
imageDroppedActionPopup = nil;
}
Note that I'm still calling release on the window, before setting it to nil.
This is by far the weirdest problem I've been stuck with.
I have a UIViewController on a UINavigationController and I want to call a method at viewDidAppear using NSInvocationOperation so it can run on a back thread when the view becomes visible.
The problem is that if I pop the view controller BEFORE the operation (in this case the testMethod method) completes running, the app crashes.
Everything works fine if I pop the view controller AFTER the operation runs it's course.
When the app crashes, it stops at [super dealloc] with "EXC-BAD-ACCESS" and gives me the following error.
bool _WebTryThreadLock(bool), xxxxxxxxx: Tried to obtain the web lock
from a thread other than the main thread or the web thread. This may
be a result of calling to UIKit from a secondary thread. Crashing
now...
And this is my code (super simplified)..
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
NSInvocationOperation *theOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:#selector(testMethod) object:nil];
[operationQueue addOperation:theOperation];
[theOperation release];
}
- (void)testMethod
{
NSLog(#"do some stuff that takes a few seconds to complete");
}
- (void)dealloc
{
[_tableView release];
[super dealloc];
}
The testMethod has some code that takes a few seconds to complete. I only have a few clues and I really don't know how and where to start debugging this.
Clue #1: The funniest thing is that if I remove the [_tableView release]; from dealloc then the app doesn't crash. But of course this would cause a leak and I can't remove it.
Clue #2: I've tested this code on a separate "clean" UIViewController with a UITableView and to my surprise it didn't crash.
Clue #3: The app doesn't crash is the UITableView's datasource is set to nil in viewDidLoad.
Clue #4: The app doesn't seem crash if I use the same code in viewDidAppear somewhere else like an IBAction.
Clue #5: I've tried looking over stack data with NSZombie but it gives me tons of data and it leads me nowhere.
I have some very complicated code within my UITableViewDelegate and UITableViewDataSource and I really don't know where to start debugging this. I really hope I don't have to go through line by line or rewrite the entire thing because of this.
Any pointers on where I should be looking?
The problem is likely that your view controller's last reference is the operation queue holding onto it, which means you are technically calling (or having the system call) some UIKit methods in a background thread (a big no-no) when the operation cleans up.
To prevent this from happening, you need to send a keep-alive message to your controller on the main thread at the end of your operation, by adding something like this to the last line in your testMethod:
[self performSelectorOnMainThread:#selector(description) withObject:nil waitUntilDone:NO];
There is still a chance that this message may get processed before the operation queue releases your view controller, but that chance is pretty remote. If it's still happening, you could do something like this:
[self performSelectorOnMainThread:#selector(keepAlive:)
withObject:[NSNumber numberWithBool:YES]
waitUntilDone:NO];
- (void)keepAlive:(NSNumber *)fromBackground
{
if (fromBackground)
[self performSelector:#selector(keepAlive:) withObject:nil afterDelay:1];
}
By sending a message to your view controller on the main thread, it will keep the object alive (NSObject retains your view controller until the main thread handles the message). It will also keep the view controller alive if you perform a selector after a delay.
You're crashing because the controller is still trying to use your tableView reference and since you poped the viewController, everything will go away in the dealloc and the tableView is still populating itself.
You can try asking in your dealloc method if your operation is still running, so you can cancel it and the everything should be fine.
Once you add an operation to a queue, the operation is out of your
hands. The queue takes over and handles the scheduling of that task.
However, if you decide later that you do not want to execute the
operation after all—because the user pressed a cancel button in a
progress panel or quit the application, for example—you can cancel the
operation to prevent it from consuming CPU time needlessly. You do
this by calling the cancel method of the operation object itself or by
calling the cancelAllOperations method of the NSOperationQueue class.
Cancelling an operation does not immediately force it to stop what it
is doing. Although respecting the value returned by the isCancelled is
expected of all operations, your code must explicitly check the value
returned by this method and abort as needed. The default
implementation of NSOperation does include checks for cancellation.
For example, if you cancel an operation before its start method is
called, the start method exits without starting the task.