Class in NSMutableArray

[Alec]

I have a class named:
Data
and it have variables:
NSString *datetime, UIImage *myPicture;
Class doesn't have any alloc or release methods for these variables.

In another class I put Data- class objects to the nsMutableArray *dataArray with addObject- method.

//Local variables
NSString *datetime;
UIImage *myPicture;
Data *myData = [[Data alloc] init];//Does nothing else than retain class

NsDate *date = [NSDate date];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@”yyyy-MM-dd HH:MM:SS];
datetime = [formatter stringFromDate:date];

//The next is coming from the camera
myPicture = [info objectForKey:UIIMagePickerControllerOriginalImage];

myData.datetime = datetime;
myData.myPicture = myPicture;

[dataArray addObject: myData];

[myData.datetime release];
[myData.myPicture release];
[datetime release];
[myPicture release];
[formatter release];
[myData release];


The question is, do I need use retain with datetime and myPicture variables(like myData.myPicture = [myPicture retain];) when I put data to myData.datetime and myData.myPicture or can nsMutableArray addObject- method retain myData.datetime and myData.myPicture variables when it retain myData- class?

[smasher]

Ask yourself at all times "who is retaining this object?" If no one is retaining an object it'll get destroyed. You're releasing too much - much too much. In this snippet the only thing you should release are formatter and myData. For now let's look at datetime instead.

//stringFromDate returns autorelease string
datetime = [formatter stringFromDate:date];

myData.datetime = datetime;

[dataArray addObject: myData];

//release the string, destroying it - it'll now crash later
//when the autorelease pool is drained or you try to access the object
[myData.datetime release];

//release the string again; will probably crash right now
[datetime release];

[myData release];

*IF* the property datetime is declared as (nonatomic,retain) -- which is what you want for objects -- then this is the correct way to do what you're doing:

//stringFromDate returns autorelease string
datetime = [formatter stringFromDate:date];

myData.datetime = datetime;

[dataArray addObject: myData];

//no need to release anything - datetime is in the autorelease pool,
//and myData is the only thing retaining it. If you had alloc/init'ed
//datetime (not gotten an autorelease string) then you would
//release it here.

//release mydata; it's being retained by the array,
//so it doesn't get destroyed
[myData release];

You should write a dealloc method for your Data class so that it can release its properties when the object gets destroyed. It'll look something like this:

-(void) dealloc{

     [datetime release];
     [myPicture release];

     [self dealloc];
}

[headkaze]

Is there a way to list the variables that still have a reference/retain count when you exit your app?

[smasher]

Originally Posted by headkaze

Is there a way to list the variables that still have a reference/retain count when you exit your app?

Yes, the "leaks" instrument will show an list (updated every few seconds) of the objects that you've "leaked" - that is, any object that is still retained but which you have no pointers to. You can also drill down to see where that object was created; then you can look at your code to figure out what's wrong with its life cycle.

[Alec]

Originally Posted by smasher

Ask yourself at all times "who is retaining this object?" If no one is retaining an object it'll get destroyed. You're releasing too much - much too much. In this snippet the only thing you should release are formatter and myData. For now let's look at datetime instead.

//stringFromDate returns autorelease string
datetime = [formatter stringFromDate:date];

myData.datetime = datetime;

[dataArray addObject: myData];

//release the string, destroying it - it'll now crash later
//when the autorelease pool is drained or you try to access the object
[myData.datetime release];

//release the string again; will probably crash right now
[datetime release];

[myData release];

*IF* the property datetime is declared as (nonatomic,retain) -- which is what you want for objects -- then this is the correct way to do what you're doing:

//stringFromDate returns autorelease string
datetime = [formatter stringFromDate:date];

myData.datetime = datetime;

[dataArray addObject: myData];

//no need to release anything - datetime is in the autorelease pool,
//and myData is the only thing retaining it. If you had alloc/init'ed
//datetime (not gotten an autorelease string) then you would
//release it here.

//release mydata; it's being retained by the array,
//so it doesn't get destroyed
[myData release];

You should write a dealloc method for your Data class so that it can release its properties when the object gets destroyed. It'll look something like this:

-(void) dealloc{

     [datetime release];
     [myPicture release];

     [self dealloc];
}

Ok, thank you. That help me a lot.