Problem decoding JSON array

WEB TMS WEB Core
1

I have a simple procedure that creates a JSON array, then tries to extract an element from it.

This proc works

procedure TForm1.WebButton1Click(Sender: TObject);
var
  j: TJsonArray;
  o: TJsonObject;
  p: TJsonPair;
begin
  j := TJsonArray.Create;
  o := TJsonObject.Create;
  o.AddPair('Field1','Value1');
  j.Add(o);

  Memo.Lines.Add(j.ToJSON);
  o := j[0] as TJsonObject;
  Memo.Lines.Add(o.ToJSON);
  p := o.Pairs[0];
  showmessage(p.JsonValue.Value);
end;

it adds the following 2 lines to the memo

[{"Field1":"Value1"}]
{"Field1":"Value1"}

an the showmessage displays "Value1"

however, the following fails

procedure TForm1.WebButton1Click(Sender: TObject);
var
  j: TJsonArray;
  o: TJsonObject;
  p: TJsonPair;
begin
  j := TJsonArray.Create;
  o := TJsonObject.Create;
  o.AddPair('Field1','Value1');
  j.Add(o);

  Memo.Lines.Add(j.ToJSON);
  o := j[0] as TJsonObject;
  Memo.Lines.Add(o.ToJSON);
  showmessage(o.Values['Field1'].Value);
end;

with the error

image
image1013×94 6.46 KB

Any ideas what I'm doing wrong ?

2

You may find this conversation useful.


Regards, Walter

3

Thanks for the link Walter.

It was an interesting read. I think it explains some of the issues I've been having. I've had to code around it by creating the JSON objects, then extracting it as a JSON string, then reparse it using TJsonObject.ParseJsonValue in order to create a collection of JSON objects that could be read using the pascal code. If I tried to access the initial JSON objects, they dont seem to be visible to pascal, but the ToJson method seems to have access to them.

I'd still be interested in hearing what TMS have to say.

4

Hello Andrew, you may find my JSON class helper useful.

JSON.pas (25.9 KB)

I wrote it because I found the existing implementation hopelessly buggy. I haven't rechecked if they fixed some bugs meanwhile though. This product luckily evolves quite fast.

Regards, Walter

5

We have fixed this issue. The next update will address this.