On Aug 5, 2010, at 7:59 AM, Graham Cox wrote:
> I have a Obj-C method that is highly recursive, and needs to run at maximum
> performance. With this in mind, I am locally caching the method's own IMP to
> avoid the message dispatch for the recursive calls. It seems to work and
> gives a measurable benefit, but I need to be absolutely certain it's right
> before committing it to a release. Can anyone comment on whether it actually
> is right? Have I missed anything? Anything even faster?
>
>
> #define qUseImpCaching 1
>
>
> - (void) recursivelySearchWithRect:(NSRect) rect index:(NSUInteger) indx
> {
> #if qUseImpCaching
> static void(*sfunc)( id, SEL, NSRect, NSUInteger ) = nil;
>
> if ( sfunc == nil )
> sfunc = (void(*)( id, SEL, NSRect, NSUInteger ))[[self class]
> instanceMethodForSelector:_cmd];
> #endif
This fails in the face of subclassing/overriding. There's exactly one instance
of this static variable, but there may be multiple results from [[self class]
instanceMethodForSelector:_cmd], depending on what the actual class of self is.
If you don't need to support subclassing and overriding of this method, just
move its body to a function, and have the method be a thin wrapper around the
function.
Regards,
Ken
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