iOS6中UDID的替代产物

 Apple对UDID废弃的声明早从iOS4开始，iOS5中需要慎重使用。而在iOS6中终于提供了UDID的替代产品identifierForAdvertising和identifierForVendor。Apple对其的描述如下：

@property(nonatomic,readonly,retain) NSUUID *identifierForAdvertising NS_AVAILABLE_IOS(6_0); // a UUID that may be used to uniquely identify the device for advertising purposes, same across apps.

Note: identifierForAdvertising会在系统reset时重新生成。

@property(nonatomic,readonly,retain) NSUUID *identifierForVendor NS_AVAILABLE_IOS(6_0); // a UUID that may be used to uniquely identify the device, same across apps from a single vendor.