iOS initWithCoder/decodeObjectForKey memory leak

Question

The Leaks instrument tells me that I have a memory leak when I use decodeObjectForKey within initWithCoder . For example:

Class.h
{
MyObject *myObject;
}

@property (nonatomic, retain) MyObject *myObject;

Class.m

@synthesize myObject

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

-(id)initWithCoder:(NSCoder *)decoder{
 if (self = [super init]{
 self.myObject = [decoder decodeObjectForKey:@"MyObject"];
 }
 return self;
}

Per request in the comments:

-(void)encodeWithCoder:(NSCoder *)encoder{

    [encoder encodeObject:myObject forKey:@"MyObject"];

}

Leaks reports a leak of type NSCFString on the line;

 self.myObject = [decoder decodeObjectForKey:@"MyObject];

As I understand it, decodeObjectForKey returns an autoreleased object. Since I immediately assign that value to the myObject property, which is specified as (nontoxic, retain) in the property definition, I retain the autoreleased object through the setter method of the myObject property. The myObject is then released in the dealloc method. I don't understand where the leak is if I understand the sequence correctly. Also why is it reported as a NSCFString when the type is MYObject?

Any thoughts would be appreciated, including if my assumptions above are correct.

Answer 1

Look carefully at your -dealloc method. You are calling [super release]; when you should be calling [super dealloc]; .

Calling [super release] in this case is the same thing as calling [self release] , since you're not overriding the -release method. If your -dealloc method is called, your object has already been fully released, so this is unnecessary. Since you are overriding the -dealloc method, you must call [super dealloc] to also free any memory allocated by the superclass.

You can refer to the NSObject documentation to see how to override dealloc correctly.