json的NSData 转换成NSDictionary

摘自：http://www.cocoachina.com/bbs/read.php?tid-254184.html

解决方法

获得的json先转换成字符串

NSString *receiveStr = [[NSString alloc]initWithData:receiveData encoding:NSUTF8StringEncoding];

字符串再生成NSData

NSData * data = [receiveStr dataUsingEncoding:NSUTF8StringEncoding];

 再解析  

NSDictionary *jsonDict = [NSJSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:nil];

就OK了