Should I release array returned from [NSMutableDictionary ValueForKey: ]

Question

I have a NSMutableDictionary with the key being the first alphabet of the name of an object. The view is something like the 'Contacts' tab on iphone. Additionally user can select individual objects in the list.

In the code I find each selected object to process them further.

NSMutableArray *objectsToAdd = [[NSMutableArray alloc] init];
NSMutableArray *array      = nil;

for (NSString *key in self.nameIndex) {

    array = (NSMutableArray *)[searchedNameDictionary valueForKey:key];    
    for (Objects *eachObject in array) {
        if (eachObject.objectIsSelected){
            [objectsToAdd addObject:eachObject];
        }
    }           
}
[array release];

-(void)dealloc()
{
    [searchedNameDictionary release];
}

The app is crashing where I release searchedNameDictionary, with the message that the deallocated object is being referenced.

Now if in the code above, I remove [array release] the app works fine.

My question is does releasing 'array' is actually releasing the objects in searchedNameDictionary, which is what seems to be happening.

Would not releasing array cause memory leak?

Answer 1

array = (NSMutableArray *)[searchedNameDictionary valueForKey:key];

This returns an autoreleased object, thus you don't need to release it.

There are some other...issues with your code too, but mostly style things. Get rid of the [array release] and you're good to go as far as that issue is concerned.

Answer 2

You shouldn't release returned object unless they come from an alloc or copy method.

Returned objects are autoreleased otherwise, if you want to keep it around your should retain it right after receiving it.