EDIT: I stuck in a single call to manually retain the array right after initializing it, and that fixed it. Dur. Thanks.
I keep an NSMutableArray in a UIScrollView subclass, and I add to it instances of a UIImageView subclass as each is added as a subview. It needs to be a mutable array, as I plan to rearrange their order in the array eventually; this bug is occurring before I even try to do so. I've used NSLogs to show that the array has count 10 up until and including applicationDidBecomeActive: is called in my AppDelegate, and added a timer to fire every 0.001s in the run loop. The first time it fires, it can't find the array anymore! I'm very confused and have been trying to track this down for hours.
The timer's working properly (i.e. when printCount: doesn't access the array, it's fine), it's only when I try to access the array there that it breaks. The regular call to printCount: below works, but the first time the timer fires I What could possibly be happening between these two calls to printCount:?
- (void)applicationDidBecomeActive:(UIApplication *)application {
NSTimer *timer = [[NSTimer scheduledTimerWithTimeInterval:0.001f
target:[viewController view]
selector:#selector(printCount)
userInfo:nil
repeats:YES]
retain];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
[[viewController view] printCount];
}
I've been endlessly stepping through the program with the debugger. The array is correct right up through this point, and its memory address is the same even after its contents are changed. However, there is only object in it afterwards -- its 10 elements get replaced by a single UITouchData instance. No idea where it comes from. None of my event-handling methods attempt to reassign the array or change it. Any ideas what could be going wrong? I'm completely mystified.
Did you -retain the array?
Perhaps your object was released? What happens if you retain it. Does that work or you just get a memory leak?
its 10 elements get replaced by a
single UITouchData instance. No idea
where it comes from.
Is it always a UITouchData instance? Always? -- Cause that would seem like a dead give-away (if its not the SAME every-time) of a memory problem.
I stuck in a call to retain to array right after initializing it, and that fixed it. Dur.
Thank you for the suggestions. As usually happens with problems like these, it was very simple and finally giving in and asking for help triggers a solution and makes me feel stupid. :D
Does the view initialize and release the array?
Are you sure that the NSView isn't released in between?
You could check if the memory address of [viewController view] (== self within printCount) is the same every time your timer calls printCount.
Related
I presume this isn't a common problem, which makes it a bit more difficult to answer. Any help is appreciated though.
I need to call this delegate a number of times in my app, and i noticed that after a number of times, the delegate starts to come back as NULL (and hence stops responding). I put an nslog everywhere the delegate gets called, so i know that at this point, it's fine:
UIImage *image = [self.delegate largeThumnailForMediaAtIndex:indexPath.row];
Then the next time this line gets called, the delegate is set to NULL. No lines around it call or set the delegate. I put an NSLog on the setDelegate method too, and that didn't get called before it changed to NULL.
Any code you might need to see, let me know. Any ideas you want me to try out, let me know about that too.
Thanks for your help.
EDIT: Bizarre, but might help to lead to a solution. I put an NSTimer scheduledTimer.. in the class which gets made the delegate, and got it to fire that once a second so I could see if it turned null at any point. The result i got, however, was that this time it didn't turn null. It returned all of the delegate methods. When i took the timer out, it goes back to returning NULL. Obviously having a timer in there is an odd workaround 'solution'. I'm hoping this rings a bell for someone and gives them a clue to where the problem might lie?
EDIT 2: I've solved this problem by, instead of using this code in my AppDelegate:
JCreateViewController *create = [[JCreateViewController alloc] init];
[create.navigationBar addLeftButtonWithTitle:#"Back" type:JButtonTypeArrow];
create.navigationBar.title = #"Entry #17";
[self.window addSubview:create.view];
Declaring it in my header file, then using this:
self.create = [[JCreateViewController alloc] init];
[self.create.navigationBar addLeftButtonWithTitle:#"Back" type:JButtonTypeArrow];
self.create.navigationBar.title = #"Entry #17";
[self.window addSubview:self.create.view];
I don't understand why this makes a difference though. I'd love to know, if anybody does know?
Looks like you're using ARC. Whatever this object is, nothing owns it. Nothing has a strong reference to it, so it gets released, and then at some point it gets deallocated.
JCreateViewController *create = [[JCreateViewController alloc] init];
This is a local variable. When the variable goes out of scope at the end of the method, you can't access that object anymore. Under MRR, this would be a leak. Under ARC, the object is going to die, just like it was in an autorelease pool.
self.create = [[JCreateViewController alloc] init];
By creating a property (presumably strong) and putting the controller into that property, you've given whatever self is an owning reference to the controller. It will now live as long as the property isn't reassigned or set to nil.
The timer fixed things because the timer retains its target (which I believe was the controller (your question is rather unclear)), and the timer itself is retained by the run loop. So the run loop keeps the repeating timer alive and the timer kept your controller alive.
In short, make sure something owns this object and it'll stick around.
Reading source code of my current project, I see:
[self retain]
in one class, in its init method.
I don't understand exactly the reason.
Reading memory management rules from Apple, I don't see anything about this, and I don't see any hypothetical [self release].
The object is asserting ownership of itself when it is initialised. The only reason I can see that this might be useful is if the object needs to guarantee its own existence until some event has happened. For example, it might run a timer and then release itself when the timer expires.
If it's not documented and there is no corresponding release, it's probably a bug.
Best guess is that the person writing the code had a retain error and this was a "quick fix" around the real problem.
This seems to be probably an error, usually it's not up to the object to retain himself.
I see only one special case: delegate and notification, where you have to be much more careful about your life cycle, but even if this case, release/retain should not be done in the object itself.
Note to Erick:
In case of UIAlert, you can release it before it has been destroyed because the view has been but in the view hiercarchy, and then referenced. So the view will be automatically destroyed when it will be removed from the view hierarchy
It's not wrong to retain self. But seeing it in an init method sounds suspicious. I can't think of a good example of where that would be a good thing to do. Also though, with ARC, you can't even do that so you'd have to think of a better way of doing things. In general, if an object is required to be alive then there would be another object that is holding onto it. Self retaining objects are prone to errors where they will never be released.
If I recall correctly some classes use the self-retain to avoid pre-mature releasing. I would say it's not exactly best practice, but if you know the rules of the game (in this case Obj-C) you can break them (sometimes).
if you have some object, it's like it have healts/ lives. when you created it , it have one live. and. function 'retain' increasing his number of lives +1, release function decreasing his number of lives -1, dealloc decreasing too, alloc increasing
After reading:
Memory management of a view controller in Objective-c
and
Does UIView's addSubview really retain the view?
I wrote the following code to toggle a subview:
#synthesize switchableView, viewSelector, currentSubview;
//...
if(switchableView.subviews.count != 0)
[[switchableView.subviews objectAtIndex:0] removeFromSuperview]]
self.currentSubview = (veiwSelector.selectedSegmentIndex == 0) ?
[ViewA new] : [ViewB new];
[switchableView addSubview:currentSubview.view];
//[currentSubview release]; //<---crashes if I uncomment this line
It seems to run fine if I comment out that release line, but I can't wrap my head around why. Here's the way I understand what happens and maybe someone can tell me where I go wrong:
So lets consider currentView:
A gets alloc-ed by the 'new' message--retain count=A:1
A gets retained by the setter--retain count=A:2
A's view gets (supposedly) retained--retain count=A:2.1
next time through...
A's subview gets released count=A:2
B gets alloc-ed by the 'new' message--retain count=B:1, A:2
A gets autoreleased by the setter-- B:1, A:1
B gets retained by the setter--B:1, A:1
nothing ever gets rid of A?
So should I change my code, or am I wrong about the way memory management works in this language...or both?-
Ok, step one, ignore the retainCount. It's one of those things Apple should rename to something like lsdjiofsudfoiwjeriowhfiuwhrteiuhweifhsdjkfhsiurwoieuriosfho so people won't guess it's name, and not list it in the documentation. For your purposes, it's entirely useless, so ignore it.
Now that I've said that, let's consider something: addSubview: DOES retain its argument, and removeFromSuperview releases the receiver.
Finally, it's hard to tell what currentSubview is. It has a view property which would lean towards a VC, however, the way you're using it by itself, would indicate its a normal view. Perhaps you can clarify so I can continue my answer.
Your understanding of retain and release is correct, as is your code. That suggests that the problem lies outside of the code you've posted. For example, you would have this problem if your currentSubView property was defined as assign instead of retain.
You code is not structured well, however. This would be much clearer:
self.currentSubView = [[ViewA new] autorelease];
Furthermore, view controllers are meant to be cached, not created and released each time the user toggles a display. Typically, you create your view controllers beforehand, and access their .view property when necessary to display the view. UIViewController will automatically deallocate non-visible views in low memory conditions, and re-allocate their view when the .view property is accessed.
Change the release line to
self.currentSubview = nil;
and I think you'll be fine. You're releasing, but not setting the property to nil. So, when it gets re-assigned next time through, release will be called again on it. But you already released it so... boom.
I Have the following code:
-(void) changeAnimation:(NSString*)name forTime:(int) times {
if(currentAnimation != #"attack")
{
id action = [CCAnimate actionWithAnimation:[self animationByName:name]];
id repeatAction = [CCRepeat actionWithAction:action times:times];
currentAction = [self runAction:repeatAction];
lastANimation = currentAnimation;
currentAnimation = name;
}
else if(currentAction.isDone)
{
//Here is where I would change the animation
//but I commented the code for now
}
}
So when I run this and click on the button that changes the animation to "attack" (by calling [mysprite changeAnimation:#"attack" forTime:1];), I get a EXC_BAD_ACCESS error from the "currentAction.isDone" line, the next time the function is called (the joystick will call changeAnimation to try and change the animation to "run" or "idle", but I want the attack animation to finish first). Any thoughts on whyI get this? currentAction is declared in my class.
Edit: there is nothing in the rest of the class that interacts with currentAction, beside a getter. Its declaration is in the .h (CCAction* surrentAction). Do I need to initialize it? I thought the returned value from runAction would be sufficient? ANyways, when I run the debugger, it is not nil, and assigned to the correct action.
Thanks,
Dave
Edit:
I ended up creating a sequence when "attacking" that calls a function that changes the currentAnimation, so i avoided the issue. Still no idea what was happening.
Here's the answer if your interested:
Other Post
More of the class is probably needed to really answer this properly, but the EXC_BAD_ACCESS typically happens because you're accessing something that has been released and is no longer available in memory.
I'm guessing that somewhere in your class you're releasing, either explicitly, or implicitly, the "currentAction" object asynchronously - and when you're checking later, it's done & gone and you're hitting this crasher.
In general, keeping a state variable or two that you always have known values on is a good way to go, and for the "actions" that you're going through, if they're asynchronous and doing their own memory management, leave them as such and work through some state variables that you maintain and control all the memory management around. It's a pretty reasonable pattern for asynchronous callbacks, either with the classic stuff or as you move into using blocks with iOS 4.0
Hey hope someone can help as I am at my wits end with this!?
I have a UISlider. I would like it to move as progress of a task takes place (playing music).
Im setting its value as the continues events happen. (progress through the track)
-(void)updateSlider:(float)value {
NSLog(#" %f ",value);
[timeIndexSlider setValue: value animated:YES];
}
Logs state that the float value is fine..
but its just doesn't move and I get the no autorelease pool - just leaking message, that you would get from a thread without one in the console. There is no thread involved on my part.
Is there a problem updating a UISlider this often?
Is there another way of controlling the sliders movement?
Cheers
I think you're getting updates on another thread and then calling into UIKit on that thread.
Try doing a performSelectorOnMainThread with a new method that does the update (maybe taking an NSNumber object).
Are you retaining a reference to the UISlider? If not, you could be calling -setValue:animated: on a nil reference. Objective-C will allow this, without actually performing the method.
This could potentially explain why you are getting the correct float value passed into the function, but are not getting any updates...
Set a breakpoint as suggested, and make sure that the UISlider reference is not nil.
If not, try posting some code so that we can take a look.
Let us know how it goes,
Tom