KVO踩过的坑

坑：-[NSNull rangeOfCharacterFromSet:]: unrecognized selector sent to instance

 

原因是change[NSKeyValueChangeNewKey]的值是NSNull，所以需要做下面的判断。

  

// 监听baoDanModel的变化

    [self.baoDanModel addObserver:self forKeyPath:@"bankAccNo" options:(NSKeyValueObservingOptionNew) context:nil];

    [self.baoDanModel addObserver:self forKeyPath:@"bankBranch" options:(NSKeyValueObservingOptionNew) context:nil];

    [self.baoDanModel addObserver:self forKeyPath:@"payBankId" options:(NSKeyValueObservingOptionNew) context:nil];