在Xcode中收到一个引用错误，说明一个对象没有定义

我正在编写解析云代码，该代码ping eBay，返回带有项目结果的JSON数据，然后解析该数据并将前两个类别存储到数组中。发送到eBay的查询是基于用户在我的iOS应用程序的itemSearch栏中输入的任何内容。当我尝试发送像"iPhone"这样的查询时，它会给我一个错误，说明如下:

ReferenceError: data is not defined
at Object.Parse.Cloud.httpRequest.success (main.js:34:11)
at Object.<anonymous> (<anonymous>:565:19) (Code: 141, Version: 1.2.18)

objective-c代码如下:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if (sender != self.nextButton) return;
    if (self.itemSearch.text.length > 0) {
        [PFCloud callFunctionInBackground:@"eBayCategorySearch"
                           withParameters:@{@"item": self.itemSearch.text}
                                    block:^(NSString *result, NSError *error) {
                                        if (!error) {
                                            NSLog(@"Successfully pinged eBay!");
                                        }
                                    }];

    }
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}

运行在Parse上的云代码(main.js)如下:

Parse.Cloud.define("eBayCategorySearch", function(request, response) {
          url = 'http://svcs.ebay.com/services/search/FindingService/v1';
  Parse.Cloud.httpRequest({
      url: url,
      params: {     
       'OPERATION-NAME' : 'findItemsByKeywords', 
       'SERVICE-VERSION' : '1.12.0',
       'SECURITY-APPNAME' : '*APP ID GOES HERE*',
       'GLOBAL-ID' : 'EBAY-US',
       'RESPONSE-DATA-FORMAT' : 'JSON',
       'itemFilter(0).name=ListingType' : 'itemFilter(0).value=FixedPrice',
       'keywords' : request.params.item,
        // your other params
     },
      success: function (httpResponse) {
          response.success(httpResponse.data)
          // count number of times each unique primaryCategory shows up (based on categoryId), return top two (done with a for loop?)
          var userCategories = {};
          data.findItemsByKeywordsResponse.searchResult[0].item.forEach(function(item) 
          {
          var id = item.primaryCategory[0].categoryId;
          if (userCategories[id]) userCategories[id]++;
          else userCategories[id] = 1;
          });
          var top2 = Object.keys(userCategories).sort(function(a, b) 
            {return userCategories[b]-userCategories[a]; }).slice(0, 2);
          console.log('Top two categories: ' + top2.join(', '));

      // deal with success and respond to query
  },
            error: function (httpResponse) {
                console.log('error!!!');
                console.error('Request failed with response code ' + httpResponse.status);
            }
       });
});

我相信这可能是因为JSON没有被正确返回，但我不确定我将如何确保，或者如何修复。任何帮助都是感激的!