-[__NSCFNumber rangeOfCharacterFromSet:]: unrecognized selector sent to instance 0x7fa5216589d0

这个算是类型的不匹配，就是把NSNumber类型的赋给字符串了自己还不知情，因为我的是测试，代码如下（viewController.m里面）

- (void)viewDidLoad {
    [super viewDidLoad];
    bankAccount = [[BankObject alloc] init];
    [bankAccount setValue:@"10" forKey:@"account"];
    [bankAccount addObserver:self forKeyPath:@"account" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil];
    
    _myLabel = [[UILabel alloc] initWithFrame:CGRectMake(100, 100, 200, 100)];
    _myLabel.text = [bankAccount valueForKey:@"account"];
    _myLabel.textColor = [UIColor whiteColor];
    [self.view addSubview:_myLabel];
    
    _myButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    _myButton.frame = CGRectMake(200, 300, 100, 50);
    _myButton.backgroundColor = [UIColor redColor];
    [_myButton addTarget:self action:@selector(changeAccount) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:_myButton];
    
}

打断点，也是程序执行完viewDidLoad后才会崩，察觉不到_myLabel.text = [bankAccount valueForKey:@"account"];这个错误，改成_myLabel.text = [NSString stringWithFormat:@"%@",[bankAccount valueForKey:@"account"]];就可以了