Cross-form variable with Multiple forms

Question

I'm a Highschool student working with Delphi 2010 and currently working on a projects. I'm having some trouble using a variable assigned a value on one form, on another whilst using "ShowModal" to view the second.

Here's what I have on the First Form (only 1 Click procedure is shown as it repeats):

  unit frmSkill_u;

    interface

    uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
      Dialogs, StdCtrls, ExtCtrls, Buttons, jpeg, dmMusiektukke_u, DBGrids, PAT, frmMusiek_u  ;

    type
     TfrmSkill = class(TForm)
    Panel1: TPanel;
    pnlBegin: TPanel;
    bitbtnMain: TBitBtn;
    pnlEasy: TPanel;
    pnlInter: TPanel;
    pnlAdv: TPanel;
    Image1: TImage;
    Label1: TLabel;
    procedure bitbtnMainClick(Sender: TObject);
    procedure pnlBeginClick(Sender: TObject);
    procedure pnlEasyClick(Sender: TObject);
    procedure pnlInterClick(Sender: TObject);
    procedure pnlAdvClick(Sender: TObject);
    private

    { Private declarations }
  public
  iLevel : integer ;
    { Public declarations }
  end;

var

  frmSkill: TfrmSkill;


implementation



{$R *.dfm}


procedure TfrmSkill.bitbtnMainClick(Sender: TObject);
begin
frmInstru.Visible := True ;
end;

procedure TfrmSkill.pnlBeginClick(Sender: TObject);
begin

   iLevel := 0 ;
 frmMusic.ShowModal ;

end;

A button will be clicked to assign which level the person can play an instrument on (Beginner level = 0) and then the second form will show using the iLevel variable in a Case statement to filter a Database according to which level the person selected.

The second form :

 unit frmMusiek_u;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, dmMusiektukke_u, Grids, DBGrids, StdCtrls, Buttons, frmSkill_u;

type
  TfrmMusic = class(TForm)
    dbgMusiekstukke: TDBGrid;
    BitBtn1: TBitBtn;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public

    { Public declarations }
  end;

var

  frmMusic: TfrmMusic;

implementation



{$R *.dfm}

procedure TfrmMusic.FormCreate(Sender: TObject);
begin
  case frmSkill.iLevel of
    0:
      begin
        with dmMusiekstukke do
        begin
           tblMusiekstukke.Filter := 'Difficulty = ''Beginner''' ;
          tblMusiekstukke.Filtered := True;
         end;
      end;
  end;

end;
end.

However, the post's method I've seen on using variable across different forms (Passing the variable to another Form) cannot work here until I figure out how to get rid of the [DCC Fatal Error] frmSkill_u.pas(7): F2047 Circular unit reference to 'frmSkill_u' error when adding "frmSkill_u" to the Uses of the second form.

How can I still use such a variable and show the second form contemporarily?

Thank you very much!

Welcome to SO! To avoid circular reference between units, you can add your frmSkill_u unit after implementation clause of second unit called frmMusiek_u. Try this! — Josef Švejk
Unfortunately, this didn't work as I think I messed up the placement of my unit names. I removed all the names and used Marc Levin's suggestion to use "Use Unit" and Delphi placed the names on all the right places, and the program is working as wished. Thank you still for your comment! — deadlyvirus

Marc Levin Marc Levin · Accepted Answer · 2018-10-14T15:17:01

I'm assuming you're a South African high school student as I was. (Using Delphi and the Afrikaans.) You used Form.Create instead of Form.Show on frm.Musiek_u;. Assuming that your form (frmMusiek_u;) has already been created. iLevel won't have a value assigned and will throw up an error.

The second thing I can see is that you have manually added all your units to your uses fields. This is a good practice to keep track of what units being used, but for the case of a PAT which I'm assuming you are doing, I would recommend going to

File -> Use Unit...

and selecting your units from there.

If you still have a problem with your PAT feel free to email me for help [email protected]

Cross-form variable with Multiple forms

1 Answers