iOS获取设备UUID

/** 
  *  生成uuid *
  *  @return <#return value description#> 
  */
-  (NSString *) uuid 
{   
     CFUUIDRef puuid  =  CFUUIDCreate( nil );    
     CFStringRef uuidString = CFUUIDCreateString( nil, puuid );   
     NSString * result  =  (NSString *)CFBridgingRelease(CFStringCreateCopy( NULL, uuidString));    CFRelease(puuid);
     CFRelease(uuidString);
     return result ;
}