Question

I have this simple class which I know is ok in terms of memory leaks.

   @interface location : NSObject {
        NSString *name;
        float lat;
        float lon;
        NSString *subtitle;
    }

    @property (nonatomic, retain) NSString *name;
    @property (nonatomic, retain) NSString *subtitle;
    @property (nonatomic, assign) float lat;
    @property (nonatomic, assign) float lon;


    @end

    @implementation location

    @synthesize name;
    @synthesize lon;
    @synthesize lat;
    @synthesize subtitle;

    -(void)dealloc{
        [name release];
        [subtitle release];
        [super dealloc];
    }

    @end

There is retain in the @property so i release in the dealloc method. Now, my question is: If I alloc one of the strings in a init method or some other method I create, should I do another release? If so, when?

@implementation location

@synthesize name;
@synthesize lon;
@synthesize lat;
@synthesize subtitle;

-(void) init{
      name = [[NSString alloc] init];
 }

-(void)dealloc{
    [name release]; // IS THIS CORRECT?!
    [subtitle release];
    [super dealloc];
}

@end 

Answer 1

If you are assigning value using self. notation then you should release (as retain was called automatically, if you use synthesize) if your were using alloc + init approach for creating new object. Example:

NSString *str = [[NSString alloc] init];
self.name = str;
[str release];

If you are assigning value using self. notation and assigning autoreleased object then you shouldn’t retain and release. Example:

NSString *str = [NSString string];
self.name = str;

If you are assigning value without self. prefix then you should not assign autorelease object and should not release, you just should alloc + init object. Example:

NSString *str = [[NSString alloc] init];
name = str;

Or if you want to assign autoreleased object without self. prefix then you should retain it. Example:

NSString *str = [NSString string];
name = [str retain];

In dealloc method you should release objects if you didn’t do that earlier.