NSString instance variable crash

Question

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!

What memory management are you using ARC, garbage collection or retain/release? — mmmmmm
– mmmmmm, Commented Mar 19, 2012 at 12:51

hamstergene · Accepted Answer · 2012-03-19 12:50:53Z

4

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.

answered Mar 19, 2012 at 12:50

hamstergene

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