Question

If I do this-

SomeObject* someObject = [[SomeObject alloc] init];
[[someObject release] release];

I presume my program wouldn’t crash because the second over-release is acting on nothing.

Whereas

[[someObject autorelease] autorelease];

would crash because the object is released twice by being passed down the chain.

This is a matter of curiousity only, I guess I’ve never had a problem with it so far.

Answer 1

(See this answer for an explanation what oneway does.)

Your first example doesn’t even compile, as void != nil. But if you simply call release two times on an object that has a retain count of 1, it’ll for sure crash.

As for why release returns void while autorelease returns id: The first says I don’t need this object any more, you may get rid of it. Thus, if it would return something and you would operate on it you’re likely to operate on a dead object. By contrast, autorelease more or less says “Soon I won’t be needing the object any more but let it stick around until I’m done with the current method.”

So as you see they are similar in that they say I won’t be needing this object any more, but they differ in the time: release says “you can get rid of the object now“, while autorelease says “you may get rid of the object later“.