ios - EXC_BAD_ACCESS when using object_setIvar -

i attempting add , set ivars on runtime class i've allocated using code below. not have experience objective-c runtime functions that's why trying learn.

    if ([object iskindofclass:[nsdictionary class]])     {         const char *classname = [aname cstringusingencoding:nsasciistringencoding];          // allocate class using class name, nsobject metaclass, , size of 0         class objectclass = objc_allocateclasspair([nsobject class], classname, 0);          // of keys in dictionary use ivars         nsdictionary *dictionaryobject = (nsdictionary *)object;         nsarray *dictionaryobjectkeys = [dictionaryobject allkeys];          (nsstring *key in dictionaryobjectkeys)         {             // convert nsstring c string             const char *ivarname = [key cstringusingencoding:nsasciistringencoding];              // add ivar class created above using key name             if (class_addivar(objectclass, ivarname, sizeof(nsstring*), log2(sizeof(nsstring*)), @encode(nsstring*)))             {                 // newly create ivar class created above using key name                 ivar ivar = class_getinstancevariable(objectclass, ivarname);                  // set newly created ivar value of key                 id value = dictionaryobject[key];                 object_setivar(objectclass, ivar, [value copy]);             }         }          objc_registerclasspair(objectclass);     } 

every time run above code exc_bad_access (code=2, address = 0x10) error on line object_setivar(objectclass, ivar, [value copy]);. don't understand why getting error. check if ivar added class before attempt set ivar's value, apparently ivar nil. i've tried nslog ivar, same error.

i tried searching on google solution, can't find information on objective-c runtime functions.

i using arc , running app on ios simulator.

you cannot set values instance variables on class. after creating , registering class can create instance of class:

id myinstance = [[objectclass alloc] init]; 

and set values instance variables on object:

for (nsstring *key in dictionaryobjectkeys) {     const char *ivarname = [key cstringusingencoding:nsasciistringencoding];      id value = dictionaryobject[key];     ivar ivar = class_getinstancevariable(objectclass, ivarname);      object_setivar(myinstance, ivar, [value copy]); }