Parsing Datasnap result using JavaScript

Question

I'm trying to return a list of data from Delphi to a listbox and I think I'm failing to grasp a fundamental of how it all fits together.

This answer has got me a working example using a locally defined dataset.

The issue I now have is the structure of the JSON object returned by my Delphi code.

In the above answer there is only 1 "tier" of data in the object:

resultJSON = '{"1":"Firm 1","2":"Firm 2","3":"Firm 3"}';

However my Delphi Code seems to add an tier. The query is as follows:

function TServerMethods1.GetFirms(jobnumb: string): TJSONObject;
var
   jso: TJSONObject;
begin
   jso := TJSONObject.Create();
   GetJobFirmList(jobnumb);
   with SQLQuery1 do
      while not Eof do
      begin
         jso.AddPair(TJSONPair.Create(FieldByName('firmref').AsString,
                                  FieldByName('firmnaem').AsString));
         Next;
      end;
   Result := jso;
end;

This returns the following result format:

 {"result":[{"1":"Firm 1","2":"Firm 2","3":"Firm 3"}]}

I either need to reduce the code outside the square braces, or understand how to iterate the levels better.

This answer here shows how to parse two tiers in a similar structure but the best I can come up with integrating the two is the following which fails:

function getJobFirms()
{
  var sel = $("#FirmList");
  sel.empty();
  var resultJSON = '{"result":[{"1":"Firm 1","2":"Firm 2","3":"Firm 3"}]}';
  var result = $.parseJSON(resultJSON);
  $.each(result, function() {      
    $.each(result.result, function(k,v) {
      var opt = document.createElement('option');
      opt.value = k;
      opt.text = v;
      sel.append(opt);
     });
  });
}

Milos Popovic · Accepted Answer · 2014-05-20 09:30:35Z

1

Like you said, it appears that you are incorrectly iterating your JSON structure. Namely, result.result is an array, so you can try something like this:

function getJobFirms()
{
    var sel = $("#FirmList");
    sel.empty();
    var resultJSON = '{"result":[{"1":"Firm 1","2":"Firm 2","3":"Firm 3"}]}';
    var result = $.parseJSON(resultJSON);
    $.each(result.result, function(i, resultItem) {
        $.each(resultItem, function(k, v) {
            var opt = document.createElement('option');
            opt.value = k;
            opt.text = v;
            sel.append(opt);
        });
    });
}

Also, if you have only one element in result.result array, you can reduce code even more:

function getJobFirms()
{
    var sel = $("#FirmList");
    sel.empty();
    var resultJSON = '{"result":[{"1":"Firm 1","2":"Firm 2","3":"Firm 3"}]}';
    var result = $.parseJSON(resultJSON);
    $.each(result.result[0], function(k, v) {
        var opt = document.createElement('option');
        opt.value = k;
        opt.text = v;
        sel.append(opt);
    });
}

edited May 20, 2014 at 9:30

answered May 19, 2014 at 16:23

Milos Popovic

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4 Comments

Dan Kelly Over a year ago

For some reason it doesn't like the parseJSON - adding an extra $.each loop gets me where I need to be. Just need to understand why Delphi/Datasnap returns in this format...

Milos Popovic Over a year ago

I'm not sure I understand. This above should work in your situation, especially when first for loop in your example doesn't seem to do anything. Also, you could reduce code even more, if you iterate (only inner loop) trough result.result[0], if that works for you.

Milos Popovic Over a year ago

Edited for another example.

Dan Kelly Over a year ago

Thanks for the examples @miloss. They both work on the JSON set as returned from the server - however there is another function (which comes with the specific Delphi examples and is used to get the JSON from the server) - that must mangle the JSON so that ParseJSON doesn't like it.

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