Which iPhone OS memory management rules and how-to's do you know?

Question

Currently I am jumping into the ice cold water called "memory management in iPhone OS".

Here's one rule i've learned:

Every time I see an alloc in my method, I will release that corresponding variable at the bottom of the method.

Every time I create an @property(...) in my header file which says copy or retain, I put a release message on that variable into the dealloc method.

Every time I have an IBOutlet, I do the same thing. Only exception: If the IBOutlet has something like @property(... assign), or in other words: If it has the assign keyword at all. Then I don't care about releasing it in the dealloc method.

I feel that there are many more good rules to know! Just write down what you have. Let's scrape them all together. Links to great descriptions are welcome, too.

Answer 1

Actually, any time you initialize an object and the method name includes "init" you are responsible for releasing it. If you create an object using a Class method that does not include the word "init" then you don't.

For example:

  NSString *person = [NSString stringWithFormat:"My name is %@", name];

does not need a release. But:

  Person *person = [[Person alloc] init];

needs a release (as you stated in your question). Likewise:

  Person *person = [[Person alloc] initWithName:@"Matt"]];

also needs a release.

This is a convention, not a rule of the language, but you will find that it is true for all Apple-supplied APIs.