Is it possible to use form attributes in separate unit? - delphi

Question

I am creating a game using delphi and want to move some of my code to a separate unit, however this code uses attributes from a form. Is this possible?
I am creating a game using a VCL form application and currently have all my code for the game algorithm in form unit. There is nothing wrong with this, as in my program runs well, except it looks messy and I have been advised to put the algorithm code in a separate unit. I have tried moving the code into a new unit, however whatever I try syntax errors appear.
This is code in my main unit where Grid is TStringGrid from the form and GridSize is a procedure from my attempted second unit:
procedure TGame.NewGame;
begin
Grid.Width:=GridSize(Grid.ColCount);
Grid.Height:=GridSize(Grid.RowCount);
end;
This is the second unit code:
unit UGameGenerator;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.Grids, Vcl.Menus,
Vcl.StdCtrls;
implementation
function GridSize(size: integer): integer;
begin
result:=291+36*(size-8);
end;
end.
EDIT:
This is code from the second unit:
procedure ClearGrid;
var
i,j: integer;
begin
for i := 0 to Grid.ColCount-1 do
begin
for j := 0 to Grid.RowCount-1 do
begin
Grid.Cells[i,j]:='';
end;
end;
end;

Answer 1

The compiler needs to find the declaration of GridSize somehow. To do that, follow this guide:
In the main form, add UGameGenerator to the uses list:
unit MainForm;
interface
uses
...,UGameGenerator; // Add here or in the implementation section
...
implementation
...
end.
In your UGameGenerator unit, expose all types/functions/procedures that is used in other program parts in the interface:
unit UGameGenerator;
interface
uses
...,...;
function GridSize(size: integer): integer;
implementation
function GridSize(size: integer): integer;
begin
result:=291+36*(size-8);
end;
end.
A tip when designing the separate unit, avoid using variables directly from other units. Instead pass them as parameters in procedure/function calls.
Otherwise you risk to have much trouble with circular references.
In your updated question, declare procedure ClearGrid( aGrid : TStringGrid); and pass the grid as a parameter.