Question

This is a follow on from another question, my question is regarding the use of the retain/release in main(). From my understanding in this simple example the retain/release statements are not needed. BUT in more complex situations its best practice to add them as it ensures that the planet instance is not released unexpectedly.

+(Planet *) planet {
    gPlanetCount++;
    //return [[[Planet alloc] init] autorelease];
    return [[[self alloc] init] autorelease];     // Better
}

int main(int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    Planet *outerMost;

    outerMost = [[Planet planet] retain];
    ...
    ... some code
    ...
    [outerMost release]; 
    [pool drain];
    return 0;
}

EDIT_001

So I could better write the above as.

int main(int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    Planet *outerMost;

    outerMost = [Planet planet];
    ...
    ... some code
    ...
    [pool drain];
    return 0;
}

cheers gary

Answer 1

Markus Müller’s comment is correct, that is, your code is correct, except for the missing pool allocation and initialization.

However, if you create an autoreleased object in a routine/method, and you use that object in that routine/method, and you are done with it, before you exit that routine/method, then there is no reason to retain it and then release it. That object is guaranteed to be retained for the duration of the life of the routine/method, and, in this case, it will most likely be released by the [pool drain] method.

You are not going to have a situation where outerMost is released unexpectedly. The expected release is in [pool drain]. It doesn’t matter how many other methods are called from within main(), as long as you are sicking to the retain/release guidelines, outerMost will not need to be retained.