Dealloc on my custom objective-C

Question

Hello.

I'm developing an iPhone application, and I very new on iPhone development.

I've created some custom classes with instance variables (NSArray, NSString, etc.). All classes inherits from NSObject.

Should I create a dealloc method to release all instance variables?

Thank you.

Answer 1

Yes, you definitely need a dealloc if you are keeping instance variables that are objects. You will also probably need to retain or copy those as well, depending on how your object creates/uses them.

Check out this article on memory management. I think it explains it pretty well. You must also read the Memory Management Programming Guide for Cocoa. Even if you don't fully understand everything, read the whole thing through, then read the article, then do some work, get some crashes and read it again :) eventually it should all click.

Answer 2

In iPhone development its pretty much SOP to have a dealloc since there is no garbage collection.

Answer 3

You have to release any object your class has ownership for. That means, yes you have to overwrite the dealloc method and release the objects there.

Normally you have ownership over values (objects) in instance variables, but it also depends own how you create them.

You should definitely read the Memory Management Programming Guide, it describes pretty well when you gain ownership.

Answer 4

Yes, having a dealloc method is normally the best way.

If you want to reclaim memory used by your instance variables you will have to release them when you are done with them. You could add a method to do this clean up:-

- (void)cleanUp {
  [myArray release];
  [myString release];
}

Call it when you no longer need the instances.

Now, the chances are that the point in time when you want to release these variables is the point in time when their parent object is destroyed (parent object is gone, so instance variables are no longer needed). As -dealloc is automatically called for you when the parent object is going to be destroyed - it makes more sense to put the cleanup code in dealloc than in our -cleanup method that we have to call at the right time.

If you don't want to reuse the memory, eg. if you are never going to be finished with the instance variables, then you don't need to release them and might not need a -dealloc.