Nsstring和NSdata的编码转换

 1、将UTF8编码转化为中文 － NSString方法  
 NSString* strAfterDecodeByUTF8AndURI = [@"%E4%B8%AD%E5%9B%BD" stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; 
2、将中文编码转化为utf8编码 － NSString方法

      NSString *y=@"http://********/成都";

      NSString  *urlstr=[y stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];    

      NSURL *url=[NSURL URLWithString:urlstr]; 

   NSURL *url = [NSURL fileURLWithPath:path];

    NSData *data = [[NSDataalloc]initWithContentsOfURL:url];

    NSString *str = [[NSStringalloc]initWithData:data encoding:NSUTF8StringEncoding];