Question

I’m using the following method in my code:

- (NSMutableArray *) newOrderedArray:(NSMutableArray *)array ByKey:(NSString *)key ascending:(BOOL)ascending {

    NSSortDescriptor *idDescriptor = [[NSSortDescriptor alloc] initWithKey:key ascending:ascending];

    NSArray *sortDescriptors = [NSArray arrayWithObject:idDescriptor];
    NSArray *orderArray = [array sortedArrayUsingDescriptors:sortDescriptors];

    [idDescriptor release];

    NSMutableArray *result = [NSMutableArray arrayWithArray:orderArray];

    return result;
}

Is this a well-coded convenience method? As I think, it returns an autoreleased NSMutableArray.

This method is called by another one:

- (id) otherMethod {

    NSMutableArray *otherResult = [[[NSMutableArray alloc] initWithCapacity:[otherArray count]] autorelease];

   // I add some stuff to otherResult and then...

    NSMutableArray *result = [dbUtils newOrderedArray:otherResult ByKey:@"objectId" ascending:NO];
    return result;
}

This method (otherMethod) is called in some view controller where I want to store returned array and release it when deallocating the view controller. However, when [result retain] is called in this view controller (because I need it to be available and I can’t allow it to be deallocated) I receive the following error:

[CFArray release]: message sent to deallocated instance

I’ve tried to log [result retainCount] just before calling retain and it print “1”. I don’t understand why an error is thrown when calling retain.

Thank you,

A

Answer 1

I don’t see anything technically wrong with the code above–otherMethod should return an autoreleased NSMutableArray. Are you sure you’re getting the error when calling retain? It looks more like you might be accidentally be sending release at some point instead of retain.

Stylistically, there’s one thing–methods with “new” in the title should always return non-autoreleased objects, so you should either name your method something else (such as orderedArray...) or use [[NSMutableArray alloc] initWithArray:] instead of arrayWithArray. Also, method signatures shouldn’t start with a capital (so ByKey should be byKey.