Question

Can we avoid objmsg function overhead by using sel and imp means selector and implementation pointer.Please tell how we can avoid it?

Answer 1

// 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.