Question

我从未做过任何类型的Web编程，但我需要请求一个JSON对象并以objective-c形式保存数据。我正在使用http://eandata.com/blog/e53/data-feed-v3---access-and-data-layout/处的文档，但我无法检索与匹配键相关联的任何字符串。我试图解析的示例JSON对象是http://eandata.com/feed/?v=3&keycode=027F74ED52886617&mode=json&find=883929215010&get=all顶级JSON对象返回三个键;地位，产品和公司。所以我访问产品密钥并将其分配给NSDictionary。在那个字典中是另一个具有关键属性的NSDictionary，所以我拿出那个字典并分配它。在属性字典内部是一个具有字符串值的关键产品。这是我需要获取的字符串，但由于某种原因，它打印为空字符串。这是相关的代码。

扫描条形码并启动GET请求

#pragma  ZBarDelegate
- (void) imagePickerController: (UIImagePickerController*) reader
 didFinishPickingMediaWithInfo: (NSDictionary*) info
{
    // ADD: get the decode results
    id<NSFastEnumeration> results =
    [info objectForKey: ZBarReaderControllerResults];
    ZBarSymbol *symbol = nil;
    for(symbol in results)
        break;

    NSString *scannedNumber = symbol.data;//@"0049000006582";
    NSString *name = symbol.typeName;
    NSLog(@"The type name is %@", name);

    NSString *eanDataExample =
    @"http://eandata.com/feed/?v=3&keycode=027F74ED52886617&mode=json&find=";
    [ eanDataExample stringByAppendingString:scannedNumber ];
    eanDataExample =
    [ eanDataExample stringByAppendingString:@"&get=all" ];

    NSURL *url = [ NSURL URLWithString:eanDataExample ];
    NSURLRequest *request =
    [ NSURLRequest requestWithURL:url ];
    connection = [ NSURLConnection connectionWithRequest:request delegate:self ];
    if ( connection ) {
        webData = [ [ NSMutableData alloc ] init];
    }
    /*resultImage.image =
    [info objectForKey: UIImagePickerControllerOriginalImage];*/

    // ADD: dismiss the controller (NB dismiss from the *reader*!)
    [reader dismissModalViewControllerAnimated: YES];
}

以下是URLConnection委托方法

#pragma NSURLConnectionDataDelegate Methods
- (void)connection:(NSURLConnection *)connection
didReceiveResponse:(NSURLResponse *)response {
    [webData setLength:0 ];

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

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
}

-(void) connectionDidFinishLoading:(NSURLConnection *)connection {
    NSDictionary *allDataDictionary =
    [ NSJSONSerialization JSONObjectWithData:webData options:0 error:nil ];
    NSArray *keys = [ allDataDictionary allKeys ];
    NSLog(@"The count of all keys is %d", keys.count);
    NSDictionary *product = [ allDataDictionary objectForKey:@"product"];
    NSDictionary *attributes = [ product objectForKey:@"attributes"];
    NSLog(@"The number of attributes are %d", attributes.count);
    NSArray *attKeys = [ attributes allKeys ];
    NSString *desc;
    for (NSString *s in attKeys) {
        if ( [ [ attributes objectForKey:s ] isKindOfClass:[NSString class ] ] ) {
            NSLog(@"The %@ object is a NSSTring", s);
        }
        NSLog(@"The att key is %@", s );
        if ( [ s isEqualToString:@"product"] ) {
            desc =
            [ attributes objectForKey:@"product" ];
            NSLog(@"The description is %@", desc);
        }
    }

}

相关日志声明。我只包括那些与我想要访问的领域相关的内容。

2013-11-17 11:25:21.254 Collections[860:60b] The product object is a NSSTring
2013-11-17 11:25:21.255 Collections[860:60b] The att key is product
2013-11-17 11:25:21.256 Collections[860:60b] The description is

Answer 1

当我尝试使用您的代码时，插入您在问题中发布的完整网址，它运行正常。您应该记录url变量，以查看您实际传递给您的请求的内容。看起来您实际上从未实际附加扫描的数字，因为这一行：

[ eanDataExample stringByAppendingString:scannedNumber ];

您没有将该表达式的值赋给任何东西。它应该是：

eanDataExample = [eanDataExample stringByAppendingString:scannedNumber];

JSON对象为具有值的键返回空字符串

1 个答案: