??????????????????????豸?????????????????????????????У?????????????????????Ч????????????棬?????????????????????????????
???????Objective-C??????????
????IOS?????У?????е????????????????????????????int??float??struct?????????????????????????????????????NSObject??????е?OC??????????????????????????????????????????????????????????????????????????????????
?????????????????????????????????????????????????????????淽????????
????????????????У????????ν??????У??????????????????????????????????????????????????????У??????????????????????????????浱?п????????????????????????в??????С???????????????????????????????????
????????????????????????????????????棬???????????????????????????????????????????????????????????????????????????????????У??????д???????????????????????????????????????????????е??????
????????????????????????????????????????????????????????????????????int????NSNumber?????????????????????????????????????????????????????????????????????NSNumer??float????????????У??????????????????е??????????????????????2??????????????????????????????????????????????????????????????????????????
??????IOS?????????У??????е????????????????????????е??????????????????????????OC???????????????????????洢???ü???????????????????????????????????????????????ж??????????????????ü????0?????????????0????????????????alloc??new????retain??????ü?????1??release??????ü?????1??
????????Objective-C??????????
????Objective-c???????????????????MRC??Mannul Reference Counting????ARC(Automatic Reference Counting)???????????????????????????????????????MRC??ARC??????????????

????1.MRC????????ü????????????????檔
????MRC???￡????е???????????????retain??release????????????檔???MRC?????????????????????????????alloc???release???retain???release??
?????????ü????0????????????????ü??????0????????????????ü????0????????л????????????й?????????ü????0??????????????????????????????????????????????????????=nil??
????2.ARC(??????ü???)???????????檔
????ARC??IOS5??????1???????ARC????????????????檔??ARC???￡?????????????????????????????????ARC???￡??????????retain??release??retainCount??????????????????dealloc????????????????[super dealloc]??????
????ARC???μ?property???????δ??strong??weak??????MRC???μ?retain??assign??strong:????retain??????????????????á?weak??????assign??????????????????????nil??????????????assign????????????????????????????????????????????