Quick question, Instruments is reporting a leak here...
MyViewController *myVC = [[MyViewController alloc] initWithNibName:#"myView" bundle:nil];
[self.navigationController pushViewController:myVC animated:YES]; //<<<<---- !00% leak according to Instruments
[myVC release];
I understand the myVC is retained by the nav controller, so I assume the nav controller releases them when the view is popped off the nav stack?
Also, there's another tricky one in one of my loops, the static analyzer is reporting a potential leak here...
//Walk through the scheduled alarms and create notifications
NSMutableArray *fireDates = [[NSMutableArray alloc] init];
for(NSDate *fireDate in fireDates) //<<<<---- Static analyzer is reporting potential leak here
{
UILocalNotification *localNotif = [[UILocalNotification alloc] init];
if (localNotif == nil)
{
[fireDates release];
return;
}
localNotif.fireDate = fireDate;
localNotif.timeZone = [NSTimeZone defaultTimeZone];
localNotif.alertBody = [NSString stringWithFormat:#"%#", alarm.Label];
localNotif.alertAction = NSLocalizedString(#"Launch", nil);
localNotif.soundName = UILocalNotificationDefaultSoundName;
localNotif.userInfo = infoDict;
localNotif.repeatInterval = NSWeekCalendarUnit;
[[UIApplication sharedApplication] scheduleLocalNotification:localNotif];
[localNotif release];
}
[fireDates release];
Do I need to somehow release fireDate?
Thanks in advance for your help!
These snippets are both fine, as snippets go. Without seeing your full code it's impossible to say if you don't do something silly elsewhere. Do you ever release your navigationController (in your app delegate -dealloc, likely)? That's a leak that doesn't mean much, but it could be what is triggering the first warning.
Edit: with regards to the second snippet, the code looks fine (though the shortcut return case will bother some coders, who would rather see a break statement). The static analyzer may be bothered by the lack of a [localNotif release] (even though it's obviously unnecessary) in the conditional return.
In the first snippet, what is being leaked? Instruments will tell you the line where it was allocated, which is often not the line "responsible" for the leak (of course, line numbers tend to be off because it gives you the return address, not the calling address). I'm assuming it's MyViewController being leaked, and that instruments is actually complaining about alloc (look in the backtrace, cmd-E I think).
If you click on the arrow next to the memory address (you might have to click around a bit and hover over the leak address; I don't remember) you'll see all the alloc/retain/release/autorelease/malloc/free/CFRetain/CFRelease calls on that address. Ignore the ones before alloc (those are for a previous object which happened to live at the same address). Match retains and (auto)releases. You can match an autorelease with the corresponding (delayed) release, because the delayed release will happen when NSAutoreleasePool is release (which is evident in the stack trace). Look for a retain without a matching (auto)release. That's the leak.
In the second case, it helps if you tell us what Clang SA is telling you (click the little triangle on the left and it expands to show you the control-flow where the leak occurs).
But I don't think the loop runs at all, because fireDates is empty.
Related
I have a leak coming from UIDeviceRGBColor. The responsible frame is +[UIColor allocWithZone:]. I am not using ARC.
The leak is coming from the method below.
- (void) lAction
{
MKCoordinateRegion mapRegion;
mapRegion.center = mapView.userLocation.coordinate;
mapRegion.span.latitudeDelta = 0.05;
mapRegion.span.longitudeDelta = 0.05;
[mapView setRegion:mapRegion animated: YES];
SettingsViewController *settingsViewController = [[SettingsViewController alloc]
initWithNibName:#"SettingsViewController" bundle:nil];
The leak is coming from this next line:
[self presentModalViewController: settingsViewController animated:YES];
Then the method finishes like this:
self.navigationController.navigationBar.tintColor = [UIColor colorWithRed:40.0/255.0
green:43.0/255.0 blue:46.0/255.0 alpha:1.0];
}
Anyone know how to fix this? Thank you all!
Try:
SettingsViewController *settingsViewController = [[[SettingsViewController alloc]
initWithNibName:#"SettingsViewController" bundle:nil] autorelease];
In order to satisfy the commenter, the explanation is simply that if you're not using ARC, whenever you call alloc, the retain count of the returned object is set to 1. You are responsible for releasing it. One easy way to do that is call autorelease on it which will automatically release it at the end of the main run loop (unless you're managing your own autorelease pool, but I won't get into that). You do want to make sure that as long as you need to use an object your code has something retaining it, in this case when you call
[self presentModalViewController: settingsViewController animated:YES];
an extra retain is called on the settingViewController, so you don't have to worry about it getting dealloced when your method finishes.
I find memory management in Objective-C pretty easy, but it does require extra code and everyone uses ARC these days. If you're just making a few small changes to an existing code base, there is no need to switch to ARC, but if you're going to continue working with the code base for some time, it will be more time efficient to switch. It is pretty straightforward to do, as Xcode will do most of the work for you. (See here: http://developer.apple.com/library/ios/#releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introduction.html).
I'm new to Objective-C and can't seem to get the memory management code right. I have the following code:
Media* myMedia = [self.myMediaManager getNextMedia];
self.navigationItem.title = [self.myMediaManager getCategory];
[self.btnImage setImage:myMedia.imageFile forState: UIControlStateNormal];
[self.lblImage setText:myMedia.imageLabel];
//[myMedia release];
My app crashes if I uncomment the above line. Do I need to do something special when I instantiate myMedia?
EDIT:
If myMediaManager is supposed to release it, when would it do that. Here is my code for getNextMedia:
- (Media*) getNextMedia {
DLog(#"Start");
Media* nextMedia = [[Media alloc] init];
[self setNextMediaIndex];
if (self.mediaIndex > -1)
{
nextMedia = [mediaArray objectAtIndex: self.mediaIndex];
}
return nextMedia;
}
EDIT2: I fixed the crashing issue (I was releasing an object I didn't own). I still see leaks and can't seem to find what the issue is.
Only objects that you own can be released.
You can release objects if you new, alloc, copy, mutableCopy or retain them first.
Since there is no alloc/copy/retain in [self.myMediaManager getNextMedia]; you can't release it.
Since myMedia is not retained here, you don't need to release it. When the origin (self.myMediaManager) releases it, it gets destroyed immediately.
NSString *string = [[NSString alloc] init];
[string release]; // now we have to release the string, since we allocated it.
NSString *string = self.navigationItem.title;
// now we don't, since it's a property of `navigationItem` and we didn't retain it.
At this point, since you are just learning, you should probably just start off using ARC with the iOS5 beta versions of XCode. It's good to have an understanding but using ARC will save you many potential pitfalls - by the time you learn enough to produce something iOS5 will be out. You can still build applications targeting iOS4, so you'll still be able to reach a lot of people.
The general rule for memory management is as follows:
For every retain, alloc, copy, or new, you need to call release or autorelease.
Since you did not call any these, you do not need to release myMedia.
For more information, take a look at this other answer I posted that deals with the subject. Also, since you are new to iOS development, I suggest looking at this answer as well.
This updated code is suspicious:
Media* nextMedia = [[Media alloc] init];
[self setNextMediaIndex];
if (self.mediaIndex > -1)
{
nextMedia = [mediaArray objectAtIndex: self.mediaIndex];
}
Depending on the condition in the if() clause, you assign a new value to nextMedia, which makes the value you just allocated unreachable, i.e. it can't be released.
Also, you don't retain the value you get from the array, so you should not release it either. But if the if() clause does not run, you still have the instance you alloc-ed, and that should be released.
That is not good. Try:
Media* nextMedia = [[Media alloc] init];
[self setNextMediaIndex];
if (self.mediaIndex > -1)
{
[nextMedia release];
nextMedia = [[mediaArray objectAtIndex: self.mediaIndex] retain];
}
You could also do (and I would prefer that):
Media *nextMedia;
[self setNextMediaIndex];
if (self.mediaIndex > -1)
{
nextMedia = [[mediaArray objectAtIndex: self.mediaIndex] retain];
}
else
{
nextMedia = [[Media alloc] init];
}
Now you can release nextMedia when that is not needed anymore, without any ambiguity about the retain count.
The Leaks Instrument in Xcode shows me an memory leak here. I have commented the affected line which Leaks is complaining about. But I see no error in my memory management...
- (void)setupViewController {
MyViewController *myVC = [[MyViewController alloc] init];
UITabBarItem *tbi = [[UITabBarItem alloc] initWithTabBarSystemItem:UITabBarSystemItemDownloads tag:1];
myVC.tabBarItem = tbi; // LEAK: 128 bytes
self.myViewController = myVC;
[myVC release];
[tbi release];
}
I mean... tbi and myVC IS released at the end, and the alloc IS balanced. So what's wrong? I don't get it.
if MyVc.tabBarItem is already set, whatever it's pointing at may not be deallocated properly, causing a leak.
It just goes to show that at least one of the following statements is true:
Instruments is not perfect and sometimes shows leaks where there aren't any (and vice versa).
Apple's code is not bug-free.
In fact, both are true.
Instruments says I have leak in this function. I am new to Obj-C so pardon for missing something obvious besides I am not sure if I am doing everything right here.
(void) selectList:sender {
NSMutableString *nibName = #"myController";
MyOwnController *study = [[MyOwnController alloc] initWithNibName:nibName bundle:nil];
study.title = #"Fundamentals";
study.listNameToLoad = #"funds";
[self.navigationController pushViewController:study animated:YES];
[nibName release];
[study.title release];
[study.listNameToLoad release];
[study release];
study = nil;
}
Related questions. Once you do pushViewController should you always do a release on the controller you just pushed on the stack ?
You should read this first.
In summary, you release only if you create or copy. You have released quite a few variables which you haven't created/copied and is not your responsibility to release. You should hence not release nibName, study.title & study.listNameToLoad.
Again, You should release the 'title' and 'listNameToLoad' properties within the controller's dealloc method.
As for your related question, you can release the controller only if you don't need the reference any more. If you do choose to keep the reference, you need to release the reference later when you don't need it any more.
I'm doing an iPhone application which uses a navigation control to browse through some data. This data is stored in a sqlite database and I have a class which gets it and returns it in a NSMutableArray of NSStrings.
The problem is that in the first screen of the navigation everything works prefectly, but in the second screen (another view which is pushed) the same code fails because the NSMutableArray gets corrupted. In the debugger I can see that it is returned correctly, but when it's time to use it the pointers have become corrupted and the application crashes.
I have put breakpoints in all my functions, and I can't see anywhere where it can get corrupted. And as the first view, which uses the same exact code, even accesing the same eact tables, works correctly I don't really know where to look.
If anyone want to have a look at the code I have uploaded it to my site: http://sachafuentes.com/iBacus.zip
Thanks in advance.
UPDATE:
The problem lies in the function where I get the data, which looks like (this is a simplified version with some pseudo-code).
-(NSMutableArray *) getPaises {
NSMutableArray * paises;
paises = [[NSMutableArray alloc] init];
while( get new row ) {
NSString *aPais = get the value;
[paises addObject:aPais];
[aPais release];
}
return paises;
}
If I comment out [aPais release] everything works, but to me this looks like a memory leak, as the NSString won't be released.
Okay, here's the problem:
NSString *aPais = [NSString stringWithUTF8String:(char*)sqlite3_column_text(compiledStatement, 0)];
By convention, any time that you see an alloc and an init, you need a release somewhere down the road.
By convention, any time that you use an xWithX: style method, the resulting object will be released for you.
Therefore, this statement:
[aPais release];
will cause your method to crash, as the object is released before it should be. Just remove this line, set your NSMutableArray instance to be autorelease-d and you should get better results.
Look for wrong memory management, that's the likeliest cause for crashes. I think you release your objects somewhere where you shouldn't and therefore you have dangling pointers in the array.
Update1
[aPais release] is wrong, as you don't retain it anywhere in this method. Returned values should always be autoreleased. You should have the same amount of retain as release in your code.
(Some people argue that a retain can also be an alloc init, but I always try to use alloc init autorelease, but this is a matter of style.)
BTW
You should autorelease your array, you're only retaining it here with [[alloc] init].
Any object that you alloc and init must be release-d when you're finished with it, or you will have a memory leak.
Since you are passing the reference outside the scope of the getPaises method, you must autorelease the NSMutableArray, or you will have a memory leak:
paises = [[[NSMutableArray alloc] init] autorelease];
Can you please clarify the step here:
NSString *aPais = get the value;
It's not clear what happens in "get the value" and I suspect this is one cause of instability.
I see that the code is (verbatim)
while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
NSString *aPais = [NSString stringWithUTF8String:
(char*)sqlite3_column_text(compiledStatement, 0)];
[paises addObject:aPais];
[aPais release];
}
...and it's exactly as #gs puts it. aPais is autoreleased and should not be released.
You can also use a convenience constructor to initialize the NSMutableArray:
NSMutableArray *paises = [NSMutableArray array];
This is equivalent to doing:
NSMutableArray *paises = [[[NSMutableArray alloc] init] autorelease];