RAC +MVVM

 https://blog.csdn.net/capf_sam/article/details/60960530

https://blog.csdn.net/capf_Sam/article/details/60960615

//响应式 <ReactiveObjc.h>
[[XXX rac_signalForSelector] subscribeNext:^(RACTuple * x){}];

//KVO <NSObject + RACKVOWrapper.h>
[XXX rac_observerKeyPath: options: observer: block:];