myFloat = 2.34f;

float myFloatValue;
object_getInstanceVariable(self, "myFloat", (void*)&myFloatValue);

NSLog(@"%f", myFloatValue);

float newValue = 2.34f;
unsigned int addr = (unsigned int)&newValue;

object_setInstanceVariable(self, "myFloat", *(float**)addr);

NSLog(@"%f", myFloat);

(int)object_getIvar(obj, myIntVar)

id returnedValue = object_getIvar(self, myIntVar);
NSLog(@"Class: %@", [returnedValue className]);

void *ptr_to_result;
object_getInstanceVariable(obj, "intvarname", &ptr_to_result);
float result = *(float *)ptr_to_result;