NSString NSURL UTF8

//把string以UTF8編碼
NSString* returnValue =
        [URLstring stringByAddingPercentEscapesUsingEncoding:
         NSUTF8StringEncoding];

例如：
//要先將中文地址轉成UTF8型式，才可做為查詢網址。
    NSString* address = [@"台北巿南港區三重路19-11號" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString: [NSString stringWithFormat:@"http://maps.apple.com/maps?q=%@",address]]];




//NSURL to NSString  NSURL
NSString *returnValue = [URL absoluteString];