ARCは遅い？

ARC vs MRC（従来のretain/release）に関するベンチマークと考察。

Confirmed: Objective-C ARC is slow. Don’t use it! (sarcasm off) | Learn & Master Cocos2D Game Development

様々な速度比較が行われているがほとんど差は無い。


ARCが遅くなると思われるケース

// this is typical MRC code:
{
    id object = [array objectAtIndex:0];
    [object doSomething];
    [object doAnotherThing];
}
 
// this is what ARC does (and what is considered best practice under MRC):
{
    id object = [array objectAtIndex:0];
    [object retain]; // inserted by ARC
    [object doSomething];
    [object doAnotherThing];
    [object release]; // inserted by ARC
}

// this is typical MRC code:
-(void) someMethod:(id)object
{
    [object doSomething];
    [object doAnotherThing];
}
 
// this is what ARC does (and what is considered best practice under MRC):
-(void) someMethod:(id)object
{
    [object retain]; // inserted by ARC
    [object doSomething];
    [object doAnotherThing];
    [object release]; // inserted by ARC
}

最後はそんなに速度が気になるならCで書けよ、みたいな（それを言ったら見も蓋もないが..）。