什么情况可能导致终止应用程序由于未捕获的类'nil'异常

Question

我的应用程序偶尔会崩溃

2012-10-10 23:19:24.039 [26442:850f] -[NSNull allKeys]: unrecognized selector sent to instance 0x7fff741cbea0
2012-10-10 23:19:24.040 [26442:850f] *** Terminating app due to uncaught exception of class 'nil'

在调用[obj isKindOfClass:[NSDictionary class]]

之前，该对象已经过allKeys:测试

如果我故意致电[[NSNull null] allKeys]，它会与

崩溃

2012-10-11 16:22:15.606 [14939:403] -[NSNull allKeys]: unrecognized selector sent to instance 0x7fff73659f00
2012-10-11 16:22:15.622 [14939:403] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNull allKeys]: unrecognized selector sent to instance 0x7fff73659f00'

我想知道导致Terminating app due to uncaught exception of class 'nil'的情况，以便我可以调试此问题。

Answer 1

1：因为NSNull没有响应消息[allKeys]，所以它会引发异常。

2：您应该检查您的对象是否可以[respondsToSelector：@selector（allKeys）]

3：如果你的NSNull类objet传递了[obj isKindOfClass：[NSDictionary class]]，那么你的控制语句就会出现问题