I was on a roll learning objective-c, but I just don't get this. I'm declaring an nsstring i-var, i set the value in the init method, and then when I access that ivar in a later instance method, it crashes or behaves unpredictably.
//heres what my declaration looks like
#interface StockData : CCNode {
NSString *myPath;
NSString *myPath2;
}
-(id) init
{
if ( (self = [super init]) ){
myPath = [[NSBundle mainBundle] pathForResource:#"stocks" ofType:#"sqlite"];
myPath2 = #"test";
CCLOG(#"mypath::::%#",[myPath class]);
CCLOG(#"mypath2::::%#",[myPath2 class]);
}
return self;
}
-(void) getChunk{
CCLOG(#"mypath_getchunk::::%#",[myPath class]);//this crashes
CCLOG(#"mypath2_getchunk::::%#", [myPath2 class]);//this doesn't
....
i am using cocos2d, and I am calling getChunk method in an scheduled update method like this:
-(void) updateOncePerSecond:(ccTime)delta{
if(!sd){
sd = [StockData initStockData];
[self addChild:sd];
}
[sd getChunk];
NSLog([sd getDate]);
}
the first time it iterates through I get this:
2012-03-19 20:33:58.591 HelloWorld[6777:10a03] mypath_getchunk::::__NSCFString
2012-03-19 20:33:58.591 HelloWorld[6777:10a03] mypath2_getchunk::::__NSCFConstantString
the second time it iterates through(if it doesn't crash):
2012-03-19 20:33:59.589 HelloWorld[6777:10a03] mypath_getchunk::::NSMallocBlock
2012-03-19 20:33:59.589 HelloWorld[6777:10a03] mypath2_getchunk::::__NSCFConstantString
why does it crash sometimes, and not other times. Why is it turning into a mallocblock? Are NSString's buggy, or am I doing it wrong. other variables seem to be working fine? How can I get my NSCFString to behave like that NSCFConstantString. I like that one better cause it doesn't crash. Any advice would be much appreciated!!!
thanks!
The string pathForResource:ofType: is autoreleased, which means it will be released “sometime later”. If you want to keep it alive, retain it:
myPath = [[[NSBundle mainBundle] pathForResource:#"stocks" ofType:#"sqlite"] retain];
And don't forget to release it later in dealloc.
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]!
I'm hoping this isn't something to do with the fact that I'm using a Mutable array here, but this one is baffling me so it wouldn't surprise me if that were the case.
BACKGROUND:
I have made a small database which is essentially an NSMutableArray containing custom objects, which we can call recordObjects. I set up the array:
database = [[NSMutableArray alloc] init];
and my custom object, called "recordObject" contains the following variables and inits:
NSString *name;
int anInt;
Bool aBool;
I also synthesized methods so I can make calls like:
aString = [[database objectAtIndex:someIndex] name];
And added methods to my controller class to add, remove, and select the individual records for display. So far everything works correctly and exactly as expected.
Next, I've set up my recordObject class (subclass of NSObject) to use the NSCoder (by including in the #interface directive, and have added the following custom encoder and decoder methods in the implementation file:
-(void) encodeWithCoder: (NSCoder *) encoder {
[encoder encodeObject: name forKey: #"recordName"];
[encoder encodeInt: anInt forKey: #"recordInteger"];
[encoder encodeBool: aBool forKey: #"recordBool"];
}
-(id) initWithCoder: (NSCoder *) decoder {
name = [decoder decodeObjectForKey: #"recordName"];
anInt = [decoder decodeIntForKey: #"recordInteger"];
aBool = [decoder decodeBoolForKey: #"recordBool"];
}
In order to write the file, I have used the following:
[NSKeyedArchiver archiveRootObject:database toFile:myPath];
When I run the program, everything APPEARS to work correctly. The encoder method is called for each of the records in the array and the file is written to disk. Opening the file with TextEdit shows that the data is there (though mostly unintelligible to me.)
THE PROBLEM:
Here's where I run into a snag.
I added the following code to LOAD the file into my database array:
database = [NSKeyedUnarchiver unarchiveObjectWithFile:myPath];
When I run the program again, this time Loading the database, it APPEARS to work correctly. My first test was to use the NSMutableArray count method:
x = [database count];
The result was that X is filled with the correct number of records in the file. If there were 5 records when I saved the database, X is set to 5 after loading the database on the next execution of the program.
Now, here's the big problem:
The program crashes if I try to use ANY of my accessor methods. For example, if I try to use the following after loading the database:
aString = [[database objectAtIndex:someIndex] name];
the program crashes and returns the following error in the console:
Program received signal: “EXC_BAD_ACCESS”.
sharedlibrary apply-load-rules all
My interpretation is that the data is not being loaded and initialized into the database array correctly for some reason, but for the life of me I can't figure out where I've gone wrong here.
As a side note, everything I've implemented came from Stephen G. Kochan's book "Programming in Objective-C"
Any ideas would be greatly appreciated!
There are a few problems with your code.
Your initWithCoder: method is not fully implemented. You must call [super init] and return self. You must also copy or retain the string object, otherwise it will be autoreleased:
- (id)initWithCoder:(NSCoder *)decoder
{
self = [super init];
if(self)
{
name = [[decoder decodeObjectForKey: #"recordName"] copy];
anInt = [decoder decodeIntForKey: #"recordInteger"];
aBool = [decoder decodeBoolForKey: #"recordBool"];
}
return self;
}
The other problem is with this line:
database = [NSKeyedUnarchiver unarchiveObjectWithFile:myPath];
That is fine, except for two things:
You're not holding a reference to the object, so it will be
autoreleased.
NSKeyedArchiver returns an immutable object, in this case an NSArray and not an NSMutableArray.
You need to do this:
database = [[NSKeyedUnarchiver unarchiveObjectWithFile:myPath] mutableCopy];
That will both retain the object (because it's a copy) and make the object an NSMutableArray.
It doesn't appear that you're initializing the recordObjects in -initWithCoder:
Try something like this:
-(id) initWithCoder: (NSCoder *) decoder {
self = [super init];
if (self){
name = [decoder decodeObjectForKey: #"recordName"] copy];
anInt = [decoder decodeIntForKey: #"recordInteger"];
aBool = [decoder decodeBoolForKey: #"recordBool"];
}
return self;
}
The data is there when you archive it but you're not properly unarchiving it.
Sounds like a memory management issue to me. EXC_BAD_ACCESS usually means that you're trying to access an object that has been deallocated. unarchiveObjectWithFile: returns an autoreleased object, so you have to retain it if you want to keep it around, either with an explicit retain or by assigning it to a retained property.
I was having the same issue when unarchiving a custom object
self.calTable = [[NSKeyedUnarchiver unarchiveObjectWithFile:calibrationFile] objectForKey:#"calTable"];
Based on Rob's answer I changed to
self.calTable = [[[NSKeyedUnarchiver unarchiveObjectWithFile:calibrationFile] mutableCopy] objectForKey:#"calTable"];
and it fixed all errors.
i have NSarray which i want to acces from all of my methods,(i want it Global), i m going to populate this array in one of my methods defined in .m file(only once).
my question is ... is it really possible to declare a NSArray in .h and define it place somewhere else or it just has to be defined when it is declared(initialization).
MY CURRENT CODE
.h file
#interface slots2ViewController : UIViewController {
NSArray* paylinesArr;
}
i m calling follwing method from ViewDidLoad
.m file
-(void)init_payline_arr
{
NSString* filePath = #"/Users/net4uonline/Desktop/slots2/paylines.txt";//filepath...
NSString *fileContents = [NSString stringWithContentsOfFile: filePath];
paylinesArr = [fileContents componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];
}
i m not able to use paylinesArr array from other methods the app crashes if follwing function is getting called
-(IBAction)ShowVal
{
NSLog(#"number of elements! %#",[paylinesArr count]);
}
Or
should i use NSMutabbleArray instead?
if you want to see then i have uploaded my desktop video while i m using debug tools!
the link to video
in this video i press the record button of the debugger(i have ns zombie enabled and the retain count as well),the app starts,i press spin button and apparently it crashes...then i show you the code which has
paylinesArr = [[fileContents componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]] retain];
which retains the paylineArr
NSMutableArray won't help you! The reason of your error is that your paylinesArr variable is autorelease variable, so probably it was deallocated before ShowVal is called. Try to retain it like
-(void)init_payline_arr {
...
paylinesArr = [[fileContents componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]] retain];
...
}
This should work. But don't forget to release it in viewDidUnload method:
- (void)viewDidUnload {
[super viewDidUnload];
...
[paylinesArr release];
}
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.
If I try and release tempSeedsArray after seedsArray = tempSeedsArray , I get an EXEC_BAD_ACCESS, and Instruments shows that tempSeedsArray has been released twice. Here is my viewWillAppear method:
- (void)viewWillAppear:(BOOL)animated {
NSString *arrayFilePath = [[NSBundle mainBundle] pathForResource:#"SeedsArray" ofType:#"plist"];
NSLog(#"HIT!");
NSMutableArray *tempSeedsArray = [[NSMutableArray alloc] initWithContentsOfFile:arrayFilePath];
seedsArray = tempSeedsArray;
NSLog(#"%u", [seedsArray retainCount]);
[seedsArray sortUsingSelector:#selector(localizedCaseInsensitiveCompare:)];
[super viewWillAppear:animated];
}
seedsArray is an NSMutableArray set as a nonatomic and a retain property, and is synthesised.
However, if I change seedsArray = tempSeedsArray to self.seedsArray = tempSeedsArray (or [self seedsArray] = tempSeedsArray etc.), I can release tempSeedsArray. Could someone please explain simply to me why this is, as I am very confused!
Thanks
seedsArray = ... assigns to the seedsArray field.
self.seedsArray = ... invokes setSeedsArray:, which is the setter for the seedsArray property.
If you #synthesize seedsArray, these two form will behave almost the same (see #JeremyP's comments below), but if you define your own setter, only the second form will set the property and invoke your code.