Gets the private variable of the parent class

Initially called method object_getinstancevariable (ID obj, const char *name, void**outvalue), use this method to actually get the value of the private variable to another class , but can only be used in non-ARC environments (configuration method: Click on the project name->build settings-> search Automatic Reference counting), my project is arc, certainly not, so I continue to find ways.

So I found this method Class_getinstancevariable (class CLS, const char *name), by this method, you can get the private variables of a class, and then through this method object_ Getivar (ID obj, Ivar Ivar) can get the value of the private variable, test it, no problem, it's done.

Member variable @interface parent:nsobject {   nsstring *string;}-(ID) init  {   if (self = [super init]) {     string = @ "Hello you";   }   return self; }//Remember import header file #import <objc/runtime.h> @interface child:nsobject@end-(void) Child {   nsstring *str;   Parent *obj = [[[Parent alloc] init];   Ivar Ivar = class_getinstancevariable ([Parent class], "string");   str = Object_getivar (obj, Ivar); Unrestricted, return value ID type   //object_getinstancevariable (obj, "string", (void *) &str);  Non-Arc use method, no return value   NSLog (@ "%@", str);}

Gets the private variable of the parent class