解决：
‘NSUnknownKeyException‘, reason: ‘[<ViewController 0x7fdf7048b200> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key label;
解决：认真检查一下label相关的线是否连接正确。
=
常见错误
原文：https://www.cnblogs.com/wwjwb/p/12609610.html
