1、本类有机会新增一个方法：
+ (BOOL)resolveClassMethod:(SEL)selOBJC_AVAILABLE(10.5,2.0,9.0,1.0);
+ (BOOL)resolveInstanceMethod:(SEL)selOBJC_AVAILABLE(10.5,2.0,9.0,1.0);
2、备援接受者
- (id)forwardingTargetForSelector:(SEL)aSelectorOBJC_AVAILABLE(10.5,2.0,9.0,1.0);
3、消息转发全流程：swift没法用
- (void)forwardInvocation:(NSInvocation*)anInvocationOBJC_SWIFT_UNAVAILABLE("");
- (NSMethodSignature*)methodSignatureForSelector:(SEL)aSelectorOBJC_SWIFT_UNAVAILABLE("");
+ (NSMethodSignature*)instanceMethodSignatureForSelector:(SEL)aSelectorOBJC_SWIFT_UNAVAILABLE("");
