objective c - Print object pointer address passed by reference -

nsstring *str = @"hello"; nslog(@"pointer = %p", str); [self dosomthingwithstring:&str];  - (void)dosomthingwithstring:(nsstring **)str {     *str = @"world";     nslog(@"pointer = %p", *str); } 

maybe it's kind of obvious question, expect have same address printed out:

pointer = 0x104ce9f40 pointer = 0x104ce9fa0 

no, should not see same address printed, because dosomthingwithstring assigns new object str caller. not modify nsstring in place.

the nsstring content "hello" referenced str no longer referenced after assignment *str = @"world", hence different printout.

perhaps better illustration separate string "world", this:

nsstring *str = @"hello"; nslog(@"pointer = %p", str);        // prints @"hello"'s address ad [self dosomthingwithstring:&str];  - (void)dosomthingwithstring:(nsstring **)str {     nslog(@"pointer = %p", *str);   // prints @"hello"'s address again     nsstring *other = @"world";     nslog(@"pointer = %p", *other); // prints @"world"'s address     *str = other;     nslog(@"pointer = %p", *str);   // prints @"world"'s address again }