Hi guys can somebody please advise how to cure the memory leaks in the code below
i've tried just about every combination of release and autorelease i can think of but every time either the app crashes or the leak remains
- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
//get refereance to the textfield
UITextField *currentTextField = (UITextField*)[self.view viewWithTag:200];
//check which picker
if(pickerView.tag ==1)
{
// Only calls the following code if component "0" has changed.
if (component == 0) {
// Sets the global integer "component0Row" to the currently selected row of component "0"
component0Row = row;
// Loads the new values for the selector into a new array in order to reload the data.
newValues = [[NSMutableArray alloc] initWithArray:[pickerData objectForKey:[selectorKeys objectAtIndex:component0Row]]];
currentValues = newValues;
// Reloads the data of component "1".
[pickerView reloadComponent:1];
}
//run the selector logic
[self textFieldDidEndEditing:currentTextField];
}
hope someone can advise
many thanks
Your problem is these two lines:
newValues = [[NSMutableArray alloc] initWithArray:[pickerData objectForKey:[selectorKeys objectAtIndex:component0Row]]];
currentValues = newValues;
The first line allocated a new instance of NSMutableArray. The second line copies the pointer from newValues to currentValues, overwriting the pointer value in currentValues. Whatever currentValues was pointing to is lost. That's the leak.
You could fix it like this:
newValues = [[NSMutableArray alloc] init...
[currentValues release];
currentValues = newValues;
This way, whatever was pointed to by currentValues has its reference count decremented before you lose access to it.
You could also solve the problem by making currentValues an Objective-C property, and using the accessor methods via self.currentValues or [self setCurrentValues:]; those methods will handle retain/release for you.
Your NSMutableArray allocation is never released.
newValues = [[NSMutableArray alloc] initWithArray:[pickerData objectForKey:[selectorKeys objectAtIndex:component0Row]]];
You should autorelease that or release it later on when you know you don't need it anymore.
Not sure how you have currentValues defined, but this should work without leaks:
In your .h file:
#property (nonatomic, retain) NSArray * currentValues;
In your .m file:
#synthesize currentValues;
self.currentValues = newValues;
Related
According to the static analyzer if we have the following property:
#property (retain, nonatomic) SomeObject * object;
and then we assign the property like so:
self.object = [SomeObject alloc] init];
a leak occurs. This makes sense because the alloc init adds +1 to the retain count and then the retaining property also increments the retain count. What is the best solution here? typically I just add an autorelease like so:
self.object = [[SomeObject alloc] init] autorelease];
But sometimes this creates problems for me and I end up over releasing the object causing my app to crash. I don't have any specific examples right now but I remember I had to take out some autoreleases cause of the application crashing. Is there something I am missing here?
EDIT: I have a concrete example now of the issue I was running into.
NSMutableArray *newData = [NSMutableArray array];
//If this is true then we are showing all of the items in that level of hierarchy and do not need to show the summary button.
if (!(contextID.count >= 1 && [[contextID objectAtIndex:contextID.count - 1] isEqual:[NSNull null]]) && contextID.count != 0)
{
GeographyPickerItem * firstItem = [[GeographyPickerItem alloc] init];
firstItem.primaryString = [NSString stringWithString:#"Summary"];
firstItem.subString = [NSString stringWithString:#""];
firstItem.isSummaryItem = YES;
[newData addObject:firstItem];
[firstItem release]; //TODO: Figure out why this is causing EXC_BAD_ACCESS errors
}
self.hierData = newData;
The code above is in the init method of a viewcontroller. HierData is a retained property, which is released in the viewControllers dealloc method. GeographyPickerItem retains the two strings, primaryString and subString and releases them in its own dealloc method. My application crashes (sometimes) when the viewControllers are de-alloced following a pop off of a navigation controller. It crashes with a EXC_BAD_ACCESS signal in the dealloc method of GeographyPickerItem (either on [substring release] or [primaryString release]).
I don't understand why this is happening because I believe I am following proper memory management guidelines. If I comment out firstItem release everything is fine.
The autorelease method you mention is fine, as is the other common idiom of:
SomeObject *thing = [[SomeObject alloc] init];
self.object = thing;
[thing release];
If you end up overreleasing later on, that is your problem. This part, which you're apparently doing correctly, is not the problem.
SomeObject * new_object = [SomeObject alloc] init];
self.object = new_object;
[new_object release];
or use ARC
check the GeographyPickerItem, if the strings properties are assign (and change to retain), or check if you always initialize them (before release).
also remember the difference of manually allocating :
[[NSString alloc] initWith...]
You must release or autorelease.
[NSString stringWith...]
No need to release.
or use ARC like meggar said
Turns out the issue was simple, my dealloc method called super dealloc at the start of the method rather than at the end. You always have to release your instance variables before you call [super dealloc]!
Alright so I am a little new to the NSMutableArray class and I think I am missing something obvious. I have an object pass a NSMutable Array to my window controller like so in my.m:
summaryWindow = [[SummaryWindowController alloc] init];
[summaryWindow setGlobalStatusArray:globalStatusArray];
I have the receiver method in the summaryWindow object as so:
-(void)setGlobalStatusArray:(NSMutableArray *)myArray
{
if ([myArray count] >0) {
if (globalStatusArray) {
[globalStatusArray release];
}
globalStatusArray = [[NSMutableArray alloc] initWithArray:myArray];
NSLog(#"Summary Window Init with new array: %#",globalStatusArray);
I see the NSLog no problem, and in that same object (summaryWindow) I have the following method:
- (NSMutableArray *)getGlobalStatusArray
{
return globalStatusArray;
}
Now I have globalStatusArray declared in my .h file as
NSMutableArray *globalStatusArray;
So shouldn't This be retained because I am using: initWithArray?
When I try to access this value in an another IBAction method:
- (IBAction)refreshButtonClicked:(id)sender
{
NSLog(#"The user has clicked the update button");
[ aBuffer addObjectsFromArray: globalStatusArray];
NSLog(#"Buffer is currently:%#",aBuffer);
[tableView reloadData];
}
The NSMutable array is null
2011-08-18 10:40:35.599 App Name[65677:1307] The user has clicked the update button
2011-08-18 10:40:35.600 App Name[65677:1307] Buffer is currently:(
)
I have tried using my own method to get the value i.e. [ self getGlobalStatusArray] to but I am missing something huge. FYI aBuffer is also declared in my .h ,
As albertamg noted, that looks like an empty array rather than nil, and a released object doesn't magically become nil under normal circumstances anyway.
This smells strongly of two different objects. Try logging self in your methods and see if one instance is getting the array and another is interacting with the UI.
This code isn't doing anything useful:
if ([myArray count] >0) {
if (globalStatusArray) {
[globalStatusArray release];
}
globalStatusArray = [[NSMutableArray alloc] initWithArray:myArray];
If the count of the old array is zero, it's leaking the actual array object. If the count is not zero, then it's releasing it properly. Just do the release and don't bother counting.
Are you sure there's actually something in myArray?
joe
As a relative Objective-C beginner, I'm obviously still not grasping certain memory management rules. I can't figure out how to make this not crash:
#interface MyClass { NSArray *playerArray4th; }
- (void) viewDidLoad { playerArray4th = [self getAudioPlayersForSoundFile:#"rimshot" ofType:#"aif"]; }
- (NSArray*) getAudioPlayersForSoundFile:(NSString*)soundFileName ofType:(NSString*)soundFileType {
//code instantiating objects....
NSArray *toRet = [[NSArray alloc] initWithObjects:toRetTickPlayer,toRetTickPlayerCopy,toRetTickPlayerCopy2,toRetTickPlayerCopy3, nil];
return toRet;
}
Then later, in a different function:
NSArray *currentArray = playerArray4th;
[currentArray release];
currentArray = nil;
currentArray = [self getAudioPlayersForSoundFile:fileName ofType:ofType];
And it crashes when trying to access the array again:
- (void) playSound:(NSString*)soundType {
AVAudioPlayer *currentPlayer;
if ([soundType isEqualToString:#"4th"]) {
if (playerArray4thCounter >= [playerArray4th count]) playerArray4thCounter = 0;
NSLog(#"Playing from array: %#",playerArray4th);
currentPlayer = [playerArray4th objectAtIndex:playerArray4thCounter];
playerArray4thCounter++;
}
}
Try to learn about properties and about using getters and setters. Don't take shortcuts unless you know exactly what's going on.
So define the playerArray4th property in your header file:
#property (nonatomic,retain) NSArray *playerArray4th;
And then in your .m file create getter/setter:
#synthesize playerArray4th;
Then, always use self.playerArray4th for assigning and getting the variable. The prior objects will be released when needed.
So this will not leak:
self.playerArray4th = [NSArray arrayWithObjects:#"text",#"text",nil];
self.playerArray4th = [NSArray arrayWithObjects:#"new array",#"text",nil];
because the second assignment releases the first array.
Furthermore, read about using autorelease. In short, if you alloc, copy or new, you should either release or autorelease. There's a lot to read about this here on SO which I will not repeat here now.
Don't forget to put self.playerArray4th = nil; in your dealloc method.
I'm programming an iPhone app and I had a question about memory management in one of my methods. I'm still a little new to managing memory manually, so I'm sorry if this question seems elementary.
Below is a method designed to allow a number pad to place buttons in a label based on their tag, this way I don't need to make a method for each button. The method works fine, I'm just wondering if I'm responsible for releasing any of the variables I make in the function.
The application crashes if I try to release any of the variables, so I'm a little confused about my responsibility regarding memory.
Here's the method:
FYI the variable firstValue is my label, it's the only variable not declared in the method.
-(IBAction)inputNumbersFromButtons:(id)sender {
UIButton *placeHolderButton = [[UIButton alloc] init];
placeHolderButton = sender;
NSString *placeHolderString = [[NSString alloc] init];
placeHolderString = [placeHolderString stringByAppendingString:firstValue.text];
NSString *addThisNumber = [[NSString alloc] init];
int i = placeHolderButton.tag;
addThisNumber = [NSString stringWithFormat:#"%i", i];
NSString *newLabelText = [[NSString alloc] init];
newLabelText = [placeHolderString stringByAppendingString:addThisNumber];
[firstValue setText:newLabelText];
//[placeHolderButton release];
//[placeHolderString release];
//[addThisNumber release];
//[newLabelText release];
}
The application works fine with those last four lines commented out, but it seems to me like I should be releasing these variables here. If I'm wrong about that I'd welcome a quick explanation about when it's necessary to release variables declared in functions and when it's not. Thanks.
Yes, you need to release them, but you need them just a little longer than beyond the end of your function.
The solution is called autorelease. Just replace release with autorelease and the objects stay around until the program gets back to the runloop.
When the program gets back there, everybody interested in one of the objects should have sent a retain message to it, so the object will not be deallocated when released by the NSAutoreleasePool.
edit actually, looking at your code, there's a lot more wrong with it. E.g. this:
UIButton *placeHolderButton = [[UIButton alloc] init];
placeHolderButton = sender;
doesn't make sense. First you allocate an object, then assign (a pointer to) it to variable placeHolderButton. That's fine.
Then you assign sender to that same variable. The reference to the object you just created is now lost.
Not sure if I get what you want, but this would be better:
-(IBAction)inputNumbersFromButtons:(id)sender {
UIButton *placeHolderButton = sender; // this is still a little useless, but ok
int i = placeHolderButton.tag;
NSString *addThisNumber = [NSString stringWithFormat:#"%i", i];
NSString *placeHolderString = firstValue.text;
NSString *newLabelText = [placeHolderString stringByAppendingString:addThisNumber];
[firstValue setText:newLabelText];
}
No allocs, so no releases necessary. The strings returned by those functions are already added to the autoreleasepool, so they will be deallocated automatically (if needed).
Well. Release them when you are done with them. The sooner the better. Some objects are tricky if you are new to memory management.
Release them in the dealloc method then.
The auto release pool can be handy, some people might disagree according to the performance issues.
you need to release anything containing the word new, alloc/init or copy.
also, you don't need to alloc/init this:
UIButton *placeHolderButton = [[UIButton alloc] init];
placeHolderButton = sender;
another way of doing this is:
UIButton *placeHolderButton = (UIButton *)sender;
in your version, it is allocating an instance with a retain count of +1, but you are immediately replacing the reference, so there is no way of releasing the memory later.
you are creating a lot of instances with alloc/init, and then replacing their references with autoreleased instances.
you could use
NSString *placeHolderString = [placeHolderString stringByAppendingString:firstValue.text];
instead of
NSString *placeHolderString = [[NSString alloc] init];
placeHolderString = [placeHolderString stringByAppendingString:firstValue.text];
which is again replacing a manually managed instance created on the first line, with an autoreleased instance on the second.
infact you could replace every alloc/init in this with the factory method and not have to deal with memory at all in it as they would be autoreleased instances.
-(IBAction)inputNumbersFromButtons:(id)sender {
//cast sender as a UIButton to suppress compiler warning, and allow us to reference it as placeholder button
UIButton *placeHolderButton = (UIButton *) sender;
int i = placeHolderButton.tag;
NSString *addThisNumber = [NSString stringWithFormat:#"%i", i];
[firstValue setText:[firstValue.text stringByAppendingString:addThisNumber]];
}
If you look at the class docs for NSString, any method with a + next to it(ie +stringWithString:(NSString *)string) is a class method, don't use these methods on a reference after you have called alloc/init on it.
I find it puzzling that you use alloc/init on a UIButton.
I always use the factory methods, e.g.
UIButton* aButton = [UIButton buttonWithType:UIButtonTypeCustom];
This returns an autoreleased button which I immediately add to its intended parent view.
Can't confirm it right now, but it looks as if the SDK caches UIButton instances and performs some optimizations behind the scenes. Every time I tried to retain a UIButton ivar, performance has degraded (especially when there is many sub views on screen)
-(void)setUserFilters{
//init the user filters array
userFilters = [[NSMutableArray alloc] init];
SearchCriteria *tmpSc= [[SearchCriteria alloc] init];
for(int i=0;i<[searchFilters count];i++)
{
tmpSc=[self.searchFilters objectAtIndex:i];
if(tmpSc.enabled==TRUE)
[userFilters addObject:tmpSc];
}
}
searchFilters is a list of filters that can be setted to true or false and I use userFilters to populate a table view with the filters that are only setted to TRUE
But the line SearchCriteria *tmpSc= [[SearchCriteria alloc] init]; causes leaks, and I don't know how to solve because if I release at the end of the function I loose my pointers and it crashes
Any ideas?
twolfe18 has made the code >much slower if searchFilters can be large. -objectAtIndex: is not a fast operation on large arrays, so you shouldn't do it more than you have to. (While true that FE is faster than objectAtIndex:, this overstated the issue and so I've striken it; see my other comments on the advantages of Fast Enumeration.)
There are a number of problems in your code:
Never create a method that begins "set" but is not an accessor. This can lead to very surprising bugs because of how Objective-C provides Key-Value Compliance. Names matter. A property named userFilters should have a getter called -userFilters and a setter called -setUserFilters:. The setter should take the same type that the getter returns. So this method is better called -updateUserFilters to avoid this issue (and to more correctly indicate what it does).
Always use accessors. They will save you all kinds of memory management problems. Your current code will leak the entire array if -setUserFilters is called twice.
Both comments are correct that you don't need to allocate a temporary here. In fact, your best solution is to use Fast Enumeration, which is both very fast and very memory efficient (and the easiest to code).
Pulling it all together, here's what you want to be doing (at least one way to do it, there are many other good solutions, but this one is very simple to understand):
#interface MyObject ()
#property (nonatomic, readwrite, retain) NSMutableArray *userFilters;
#property (nonatomic, readwrite, retain) NSMutableArray *searchFilters;
#end
#implementation MyObject
#synthesize userFilters;
#synthesize searchFilters;
- (void)dealloc
{
[searchFilters release];
serachFilters = nil;
[userFilters release];
userFilters = nil;
[super dealloc];
}
- (void)updateUserFilters
{
//init the user filters array
// The accessor will retain for us and will release the old value if
// we're called a second time
self.userFilters = [NSMutableArray array];
// This is Fast Enumeration
for (SearchCriteria *sc in self.searchFilters)
{
if(sc.enabled)
{
[self.userFilters addObject:sc];
}
}
}
It seems that your initially creating a SearchCriteria object and before you use it or release it your reassigning the variable to another object from self.searchFilters. So you don't need to create the initial object and why it's leaking and not being released.
Try:
SearchCriteria *tmpSc = nil;
Hope that helps.
first of all, the worst n00b code you can write involves if(condition==true) do_something(), just write if(condition) do_something().
second, there is no reason to have tempSc at all (never mind alloc memory for it), you can just do the following:
-(void)setUserFilters{
//init the user filters array
userFilters = [[NSMutableArray alloc] init];
for(int i=0;i<[searchFilters count];i++)
{
if([self.searchFilters objectAtIndex:i].enabled)
[userFilters addObject:[self.searchFilters objectAtIndex:i]];
}
}