Objective C pointer to pointer - how to distinguish passing nil vs not initialized variable set to nil -

i have method accepts pointer pointer param:

+(void)somemethod:(nsstring*_nullable*_nullable)parsed; 

now, if call method , pass "nil" parameter, , dereference inside of method like:

*parsed = soemthing; 

i crash bad access. question is, how construct condition distinguish passing "nil" vs passing not initilized variable like:

nsstring* s; // technically nil too, dereference works , doesn't crash [someobj somemethod:&s]; 

to prevent crash mentioned in first case.

the solution relatively simple, should never pass uninitialized variable. consider doing this:

nsstring *s = nil; [someobj somemethod:&s]; 

note &s have declared somemethod require nsstring **. doing &s parsed defined, variable stored somewhere in memory. value, stored @ *parsed have been initialized nil. should able things like:

+(void)somemethod:(nsstring* _nullable *_nullable)parsed {     if( null != parsed ) {         if( nil == *parsed ) {             *parsed = @"our variable *s set!";         }     } } 

enjoy!