- (void)viewDidLoad {
    [super viewDidLoad];
    
    Person *person = [[Person alloc] init];
    NSLog(@"%tu", person.retainCount); // 2015-12-31 09:57:31.003 01-引用计数练习[2014:46979] 1
    Person *anotherPerson = [person retain];
    NSLog(@"%tu", person.retainCount); // 2015-12-31 09:57:31.003 01-引用计数练习[2014:46979] 2
    [anotherPerson release];
    NSLog(@"%tu", person.retainCount); // 2015-12-31 09:57:31.003 01-引用计数练习[2014:46979] 1
    //这次release完了以后 对象就被释放了, 但是retainCount仍然是1
    [person release];

    //为什么对象被释放了以后, 还能打印出他的类型
    NSLog(@"%@", person); //2015-12-31 10:01:15.624 01-引用计数练习[2062:50220] <Person: 0x7fd84151e680>
}

那么问题来了....

为什么对象被释放了, 仍然能打印出来呢....
求解..