iOS runtime和kvc的相同运用 访问对象的私有属性

Person.h
@property (strong , nonatomic) NSString *name;
Person.m
@property (strong , nonatomic) NSString *age;

怎样需要访问Person类中的私有属性age？

方法1 通过KVC访问

    Person *p = [[Person alloc]init];
    //赋值
    [p setValue:@"26" forKeyPath:@"_age"];
    //取值
    NSString *age = [p valueForKeyPath:@"_age"];
    NSLog(@"age = %@",age);

方法2 通过runtime访问

    Person *p = [[Person alloc]init];
    //获取对象的私有属性
    Ivar ivarName = class_getInstanceVariable([p class], "_age");
    NSLog(@"属性名:%s",ivar_getName(ivarName));
    //给成员变量赋值
    object_setIvar(p, ivarName, @"52");
    NSLog(@"age = %@",object_getIvar(p, ivarName));