CFStringRef和NSString之间的转换

转自:http://www.jianshu.com/p/4ba0b0cefe95

找了半天，没有找到，结果在stackoverflow网站找到. 

很简单：

Typically NSString *yourFriendlyNSString = (__bridge NSString *)yourFriendlyCFString;

and

CFStringRef yourFriendlyCFString = (__bridge CFStringRef)yourFriendlyNSString;

引自：http://stackoverflow.com/questions/17227348/nsstring-to-cfstringref-and-cfstringref-to-nsstring-in-arc