Objective-C Memory Management: crash on release

Question

I\'m new to Objective-C and can\'t seem to get the memory management code right. I have the following code:

Media* myMedia = [self.myMediaManager getNextMedia];
         


        

Answer 1

This updated code is suspicious:

Media* nextMedia = [[Media alloc] init];

[self setNextMediaIndex];

if (self.mediaIndex > -1)
{
    nextMedia = [mediaArray objectAtIndex: self.mediaIndex];
}

Depending on the condition in the if() clause, you assign a new value to nextMedia, which makes the value you just allocated unreachable, i.e. it can't be released.

Also, you don't retain the value you get from the array, so you should not release it either. But if the if() clause does not run, you still have the instance you alloc-ed, and that should be released.

That is not good. Try:

Media* nextMedia = [[Media alloc] init];
[self setNextMediaIndex];
if (self.mediaIndex > -1)
{
    [nextMedia release];
    nextMedia = [[mediaArray objectAtIndex: self.mediaIndex] retain];
}

You could also do (and I would prefer that):

Media *nextMedia;
[self setNextMediaIndex];
if (self.mediaIndex > -1)
{
    nextMedia = [[mediaArray objectAtIndex: self.mediaIndex] retain];
}
else
{
    nextMedia = [[Media alloc] init];
}

Now you can release nextMedia when that is not needed anymore, without any ambiguity about the retain count.