Parsing a Json array in Delphi

Question

I have a problem to parse an array in Json. The Json is like this example:

and so on.

I get always an access violation error if I try to parse it:

procedure tform1.test;
var
 i:integer
 value,A:string;
 jValue:TJSONValue;
 JSonValue:TJSonValue;
 Jarray:TJSONArray;

 begin
 jValue:=RESTResponse1.JSONValue;
 Jarray := TJSonObject.ParseJSONValue(value) as tjsonarray;
 for i := 0 to Jarray.Count - 1 do
 A:=Jarray.items[i].value;
 end;

What am I doing wrong?

Use your debugger and find out exactly where the error is.

David Heffernan
– David Heffernan

2019-11-24 22:06:35 +00:00
Commented Nov 24, 2019 at 22:06 — David Heffernan
– David Heffernan, Commented Nov 24, 2019 at 22:06

John I · Accepted Answer · 2019-11-25 13:24:18Z

2

Use JsonValue as TJSONArray twice. A working example:

procedure TForm1.Test1;
var
  I: Integer;
  Value, A: String;
  jValue: TJSONValue;
  JSonValue1, JSonValue2: TJSonValue;
  JArray, JArr: TJSONArray;
begin
  Value  := '[["A1","A2","A3"],["B1","B2","B3"]]';
  JsonValue1 := TJSonObject.ParseJSONValue(Value);
  try
    JArray := JsonValue1 as TJSONArray;
    for JsonValue2 in JArray do
    begin
      JArr := JsonValue2 as TJSONArray;
      A := JArr.Items[0].Value;
      ShowMessage(A);
    end;
  finally
    JsonValue1.Free;
  end;
end;

edited Nov 25, 2019 at 13:24

answered Nov 24, 2019 at 23:29

John I

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2 Comments

Remy Lebeau Over a year ago

You need to Free() the TJSONValue that ParseJSONValue() returns. So use another TJSONValue variable for the loop

John I Over a year ago

@Remy Lebeau Thanks for the suggestion, I corrected.

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