json, how to handle an empty value?

[Nicole]

here is a method, which fomats json:

Code: Pascal  [Select][+][-]

1. function TKurse_prep.FormatiereSuche (JsonArray: TJSONArray): string;
2. var i: Integer;
3.     Symbol, Name, Currency, StockExchange, ExchangeShortName: string;
4.     JsonObject: TJSONObject;
5. begin
6.   Result := '';
7.  
8.   for i := 0 to JsonArray.Count - 1 do
9.   begin
10.     JsonObject := JsonArray.Items[i] as TJSONObject;
11.  
12.     // Zugriff auf spezifische Felder mit 'Find' - Fehlerbehandlung für fehlende Felder
13.     Symbol := JsonObject.Find('symbol').AsString;
14.     Name := JsonObject.Find('name').AsString;
15.     Currency := JsonObject.Find('currency').AsString;
16.     StockExchange := JsonObject.Find('stockExchange').AsString;
17.  
18.     ExchangeShortName := JsonObject.Find('exchangeShortName').AsString;
19.  
20.     // das macht Probleme, uU ist es leer
21.  
22.     // Ergebnis auch dann hinzufügen, wenn eines der Felder fehlt
23.     Result := Result + IntToStr(i) + ': Symbol: "' + Symbol + '", Name: "' +
24.              Name + '", Währung: "' + Currency + '", Börse: "' +
25.              StockExchange + '", Börsenkürzel: "' + ExchangeShortName + '"' + #13#10;
26.   end;
27.  
28.   Result:=trim(result);
29.   if Result = '' then Result := 'Keine Ergebnisse gefunden.';
30. end;

Works find, although somtimes this line gives me a error-message "must not be zero".

Code: Pascal  [Select][+][-]

1. StockExchange := JsonObject.Find('stockExchange').AsString;

How to avoid an error message and just leave out this very string?

[Gustavo 'Gus' Carreno]

Hey Nicole,

If you use a TJSONData first, then you have access to FindPath, which will return a nil if the node/path, is not present, which is what I think you're getting.

This has been my way of avoiding issues when some fields are missing:

Code: Pascal  [Select][+][-]

1. var
2.   JSONData: TJSONData;
3.   JSONObject: TJSONObject;
4. begin
5. { ... }
6.   JSONData:= JSONArray.Items[i] as TJSONData;
7.   JSONObject:= JSONData.FindPath('stockExchange');
8.   if Assigned(JSONObject) then
9.     StockExchange:= JSONObject.AsString;
10. { ... }
11. end;

I think this should solve your problem.
But please double check my code. I did not run this on the IDE, I just typed from memory.

Cheers,
Gus