仅仅作为一个warning记录笔记
1.属性在子类中重复定义。
Auto property synthesis will not synthesize property 'isLoaded'; it will be implemented by its superclass, use @dynamic to ackn...
解决方案：
-去掉子类中的属性。
-外面权限写成readonly，里面的写成readwrite。
2.masory约束存在问题
Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
3.命名规范问题：
property follows cocoa naming convention for returning 'owned' objects
属性不能以关键字符开头。记得以前刚学OC的时候看到过，不能以alloc，new，copy，mutableCopy 作为开头命名，比如：newPassword, 小细节没注意就会犯错。
4.delegate子类重复声明
Auto property synthesis will not synthesize property 'delegate'; it will be implemented by its superclass, use @dynamic to acknowledge intention
如何写delegate的继承
