Avoid objmsg function overhead?

Can we avoid objmsg function overhead by using sel and imp means selec开发者_开发知识库tor and implementation pointer.Please tell how we can avoid it?

// first, access the SELector you're interested in (example)
SEL sel = @selector(<#SOMETHING#>);

// this is the definition of IMP
id (*IMP)(id, SEL, ...);

access the IMP for an instance of a specific class using: + (IMP)instanceMethodForSelector:(SEL)aSelector;

ideally, you will cast the result of instanceMethodForSelector: to an exact typedef of the function you call so the compiler can get the sig right.

once you have the object, SEL and IMP, then use the IMP as an ordinary C function pointer.

where the first message to the IMP function returned is the object(=self), and the second argument is the selector(=_cmd). these are the 2 hidden objc arguments.

I assume that you requirement is a result of profiling, and not a case of premature optimization.

1) You can fetch method's implementation (see Justin's answer). To elaborate - there is no much overhead in objc_msgSend. Most of the time it will check for nil value of self, search for IMP in cache and perform a tail call to IMP ( http://www.friday.com/bbum/2009/12/18/objc_msgsend-part-1-the-road-map/ ). If you want to save this few instructions then ...

2) ... write your function in C from the start. It is much more readable and reliable solution.

The only serious answer to this question is

Use something other than Objective-C

Honestly, any way to avoid obj_msg_send() is guaranteed to be fragile and will probably save you nanoseconds per call. If you do have a very short function that is called very frequently, then you should probably just use C to reimplement that function. In almost all other cases, it's not worth the bother.