Question

I have been searching through the web and reading many posts, but none has yet to explain me how this exactly works. I know that the convention says that any method must return an autoreleased object (except for alloc, new, copy and mutableCopy) so something like this is fine:

-(MyClass*)findRandomName { return [[[MyClass alloc] initWithString:@"Something"] autorelease]; }

My question is, should I also call autorelease on the return value if I use a convenience method, or something similar? like here:

-(MyClass*)findRandomName { return [[MyClass startFromString:@"Something"] autorelease]; }

And why, or why not ? Thanks in advanced.

Answer 1

Your first example is incorrect as it should call [MyClass alloc] before calling initWithString, e.g.:

-(MyClass*)findRandomName { 
    return [[[MyClass alloc] initWithString:@"Something"] autorelease]; 
}

In the second example you should not autorelease the object. The startFromString method should already autorelease the object and if you autorelease it again you will over release the object.

In the second example the findRandomName method does not take ownership of the object (because the method it calls does not contain alloc, new, copy or mutableCopy in the name) so it should not release the object.

Your statement that “the convention says that any method must return an autoreleased object (except for init, new and copy)” is not quite correct. The memory management policy says:

You own any object you create

You create an object using a method whose name begins with “alloc”,
“new”, “copy”, or “mutableCopy” (for example, alloc, newObject, or
mutableCopy).