isKindOfClass：方法指示对象是给定类的实例还是该类的子类的实例。

The isKindOfClass: method indicates whether an object is an instance of given class or an instance of a subclass of that class.

if ([instance1 isKindOfClass:[CustomUIViewController class]]) {
    // code
}

如果要检查对象是否是给定类的实例（但不是a的实例）该类的子类），改为使用 isMemberOfClass：。

If you want to check whether an object is an instance of a given class (but not an instance of a subclass of that class), use isMemberOfClass: instead.