iphone - 无法从 NSURLConnection 响应中解析 JSON 数据

Question

我收到以下形式的服务器响应:

results are:{
    AverageMark = 40;
    "Grade A" = 10;
    "Grade B" = 20;
    "Grade C" = 30;
    "Grade D" = 20;
    MaxMark = 99;
    MinMark = 44;
    ProfileGrade = "";
    ProfileMark = 1;
}

但是我无法将响应数据保存到数组中。这是我在 didReceiveResponse 中的代码:

    {    
        NSString *jsonString = [[NSString alloc] initWithString:responseData];
        NSArray *jsonResults = [jsonString JSONValue];
        NSLog(@"results are:%@",jsonResults); //this log is shown above
        for (int i=0; i<[jsonResults count]; i++)
        {
            NSDictionary *AllData=(NSDictionary *)[jsonResults objectAtIndex:i]; //Program is crashing here--//
            NSMutableArray  *DataArray=[[NSMutableArray alloc]init];
            NSString *avgMarkString;
            avgMarkString=(NSString *)[AllData objectForKey:@"MaxMark"];
            [DataArray addObject:avgMarkString];
        }
    }

我想将响应数据保存到名为“DataArray”的数组中。但是程序崩溃了。我做错了什么？

Answer 1

-connection:didReceiveResponse: 中您可能还没有完整的数据。创建类型为 NSMutableData 的实例变量或属性，并初始化
中的数据 ivar 或属性-connection:didReceiveResponse: 如果您获得有效的状态码(200-299 之间应该没问题)。在 -connection:didReceiveData: 委托(delegate)方法中对数据对象使用 appendData:。终于在-connectionDidFinishLoading:中数据完整，可以解析成JSON了。

或者你可以只使用 AFNetworking图书馆。该库有一些方便的方法来处理 XML、JSON、图像等...

阅读以下页面以了解 AFNetworking 的功能:http://engineering.gowalla.com/2011/10/24/afnetworking/

---

一些示例代码来 self 自己的一个项目，用于使用 NSURLConnectionDelegate 方法使用队列进行下载。 URL Request 对象是一些 block “回调”的 NSURLConnection 的自定义子类:

#pragma mark - URL connection delegate

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;

    NSRange range = NSMakeRange(200, 99);
    if (NSLocationInRange(httpResponse.statusCode, range));
    {
        self.data = [[NSMutableData alloc] init];
    }
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [_data appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    // inform caller that download is complete, provide data ...

    if (_request.completionHandler)
    {
        _request.completionHandler(_data, nil);
    }

    [self removeRequest:_request];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    DLog(@"%@", error);

    // inform caller that download failed, provide error ...

    if (_request.completionHandler)
    {
        _request.completionHandler(nil, error);
    }

    [self removeRequest:_request];
}