ReactiveCocoa(RAC) Sample Code #1-Primary class

• RACSignal
• RACSubject
• RACReplaySubject

#2-Common usage

• replace Delegate
• replace KVO
• observe Event
• replace Notification
• observe TextField
• resolve Multiple Requests

#3-Common macro

• RAC(TARGET, [KEYPATH, [NIL_VALUE]])
• RACObserve(TARGET, KEYPATH)
• @weakify(Obj) & @strongify(Obj)