Member reference type ‘struct objc_class *‘ is a pointer; maybe you meant to use ‘->‘?
Definition of ‘struct objc_class‘ must be imported from module ‘ObjectiveC.runtime‘ before it is required
在类方法中（ +(void)...... ）不能使用self.
因为此时还没有创建出自己的对象
原文：http://www.cnblogs.com/shen5214444887/p/4921221.html