Question

Can you describe the naming convention difference between a method that returns an object it has allocated for the caller (and that the caller should release), and a method that returns an autorelease object?

If you declare a property with a retain attribute, do you need to release the property before you set it to nil?

What does the @synthesize directive do?

Answer 1

A good source for memory allocation is listed below by Aaron.

Regarding @synthesize:

Say you have a property P, what you will have to do is write a getter and a setter for it. There are a few common approaches, one of which is that you retain that object when you set that property and release the old value. E.g:

- (void)setP:(PClass *)value
{
  [value retain];
  [_pInstanceVariable release];
  _pInstanceVariable = value;
}

Since this is a very common piece of code, the compiler can automate it for you, if you specify the retain keyword in property declaration and then do the @synthesize in you implementation. The compiler will generate the above mentioned code which means your code will be a lot cleaner without tedious repeating parts.

Same holds true for getters, unless you want something more complex than:

- (PClass *)p
{
  return _pInstanceVariable;
}

the @synthesize will do the job