Lazarus Pascal

Demonstrates how to Handle Large Integers in JSON

See more JSON Examples

Demonstrates how to handle large integers in JSON. (Integers larger than what can fit in a 32-bit signed integer.) Lazarus Pascal

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  json: TJsonObject;
  id: Integer;
  accountId: string;

begin
  success := False;

  //  Let's say your JSON has this:

  //  {
  //  	"id": 20000000001234567
  //  }

  json := TJsonObject.Create;

  success := json.LoadFile('qa_data/json/large_int.json');
  if (success = False) then
    begin
      WriteLn(json.LastErrorText);
      Exit;
    end;

  //  The integer is too large for a 32-bit signed integer that is returned by IntOf.
  //  The result will be something that wrapped around and could be negative.
  //  In this case it would be: -543893881
  id := json.IntOf('id');
  WriteLn('id: ' + id);

  //  The solution is to read the integer value as a string, and then use the features in your programming language
  //  to convert from a string to a 64-bit integer.
  //  
  //  Alternatively, you may wish to simply hold the value as a string.  If, for example, the integer simply references
  //  an order ID, an account ID, etc., then there's no need to convert to an integer value.  You're not going to be doing
  //  mathematical operations on it anyway.  This is usually the case for large integers -- they typically exist
  //  in JSON as an account ID.

  //  You can get any JSON value as a string:
  accountId := json.StringOf('id');
  WriteLn('accountId: ' + accountId);

  //  Sample output:

  //  id: -543893881
  //  accountId: 20000000001234567


  json.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.