DELPHI - How to call stored procedure (TFDStoredProc)

TFDStoredProc with one input parameter and with integer return value.

var
  iGraphCount : integer;
  pStoredProc : TFDStoredProc;
begin
  ...
  { -- get graphs count }

  pStoredProc := DB.GetStoredProc( 'sql_detail_graphs_exists_by_SQL_ID' );
  try
    pStoredProc.ParamByName( '@sql_id' ).AsInteger := self.GetQuestion_Info.iSQL_ID;

    DB.CallStoredProc( pStoredProc );

    iGraphCount := pStoredProc.ParamByName( '@return_value' ).AsInteger;
  finally
    pStoredProc.Free;
  end;

function TDB.GetStoredProc( _sName : string ) : TFDStoredProc;
var
  pStoredProc : TFDStoredProc;
begin
  pStoredProc := TFDStoredProc.Create( Application );

  try
    pStoredProc.Connection := FDConnection;
    pStoredProc.StoredProcName := AnsiUpperCase( _sName );
    pStoredProc.Prepare;
  except
    on E : Exception do
      begin
        MessageDlg( 'Stored procedure error: ' + #13 + #13 +
                     E.Message, mtError, [ mbOk ], 0 );
      end;
  end;

  result := pStoredProc;
end;

procedure TDB.CallStoredProc( _pStoredProc : TFDStoredProc; _bOpen : boolean = false );
begin
  if _pStoredProc = nil then exit;

  if ( not _bOpen ) then
    _pStoredProc.ExecProc
  else
    _pStoredProc.Open;
end;