Question

My object has a private NSMutableArray items. I am using the following code to sort the objects in items in size order:

-(void)sortItems{
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"size" ascending:YES];    
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
NSArray *sortedArray = [items sortedArrayUsingDescriptors:sortDescriptors];
NSMutableArray* newArray = [[NSMutableArray alloc] initWithArray: sortedArray];
[self setItems:newArray];
[sortDescriptor release];   

}

Obviously this is a memory leak here, because every time I call sortItems, I am allocing new memory and assigning items to point to it. I’ve tried releasing the old memory as follows:

NSMutableArray* newArray = [[NSMutableArray alloc] initWithArray: sortedArray];
NSMutableArray* oldArray = [self items];
[self setItems:newArray];
[oldArray release];

But that gives an EXC_BAD_ACCESS error. I’ve read up on memory handling in objC, and I’m convinced I’m doing something fundamentally wrong here.

Any help would be greatly appreciated!

Answer 1

You’re leaking the new array, not the old one:

NSMutableArray* newArray = [[NSMutableArray alloc] initWithArray: sortedArray];
[self setItems:newArray];
[sortDescriptor release];
[newArray release]; // <-- add this

The fundamental rule is that you must release anything that you have allocated, and you normally shouldn’t care about keeping things retained for anyone (i.e. [self setItems:]), those who need something retained will do it themselves.

I would also recommend making self.items a mutable array, and using [self.items sortUsingDescriptors:sortDescriptor to sort inplace without creating a copy.