Can't pass a variable between two forms

[Bul the noob]

I have two forms. Both "use" each other (after "implementation"). The first unit has some variables, but the second one reads them...weird. If the variable has its value assigned in the formcreate procedure (of the first form), it uses that value. If the value is changed in any other procedure, be it buttonclick or a custom procedure, it ignores it and uses the value assigned in formcreate (or 0). Any ideas what could be wrong?

[Never]

you might named your vars with the same name of another var or property and you think you are reading the correct one
if this is the case transform them to public properties this way you will be forced to use the full name frm1.sharedprop1 in order to read the correct value

[Leledumbo]

My crystal ball shows nothing... (read: show your code)

[Windsurfer]

It is most likely that you do not understand 'scope'.

The variable defined in the initialization section is global. (global scope)

A variable defined in a procedure or function is only visible within the procedure or function. (local scope)

Therefore a local variable ,say an integer called 'I', can be defined and used in every procedure  but it is a different variable in each, and is destroyed as the procedure is closed.

[Bul the noob]

They have unique names and they are all global variables. I didn't originally post code because it is long and uses lot of objects and I hoped someone would be familiar with this specific behavior, but as I see I was wrong, so here it is (with added comments for you; it is a chess):
Form 1:

Code: [Select]

unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ExtCtrls,
  StdCtrls;

type

  { TForm1 }

  TForm1 = class(TForm)
// Images: Image1 - one big image in the back, serves to show the board
// pieces are images above above the board, named as acronyms (e.g. BR# - a black rook)
// sel - serves to highlight the selected piece
// the top layer are 64 fields, named as they are in chess (A1-H8), 64x64 in size
    BT1: TImage;
    sel: TImage;
    WP1: TImage;
    WT1: TImage;
    BP1: TImage;
    BH1: TImage;
    WP2: TImage;
    WH1: TImage;
    BP2: TImage;
    BB1: TImage;
    WP3: TImage;
    WB1: TImage;
    BP3: TImage;
    BK: TImage;
    WP4: TImage;
    WK: TImage;
    BP4: TImage;
    BQ: TImage;
    WP5: TImage;
    WQ: TImage;
    BP5: TImage;
    BB2: TImage;
    WP6: TImage;
    WB2: TImage;
    BP6: TImage;
    BH2: TImage;
    WP7: TImage;
    WH2: TImage;
    BP7: TImage;
    BT2: TImage;
    WP8: TImage;
    WT2: TImage;
    H7: TImage;
    A2: TImage;
    F2: TImage;
    B2: TImage;
    C2: TImage;
    D2: TImage;
    E2: TImage;
    G2: TImage;
    A1: TImage;
    B1: TImage;
    C1: TImage;
    G7: TImage;
    D1: TImage;
    E1: TImage;
    BP8: TImage;
    Image1: TImage;
    H1: TImage;
    G1: TImage;
    F1: TImage;
    A8: TImage;
    C8: TImage;
    D8: TImage;
    B8: TImage;
    F7: TImage;
    E8: TImage;
    H8: TImage;
    G8: TImage;
    F8: TImage;
    A3: TImage;
    B3: TImage;
    C3: TImage;
    D3: TImage;
    E3: TImage;
    F3: TImage;
    E7: TImage;
    G3: TImage;
    H3: TImage;
    A4: TImage;
    B4: TImage;
    C4: TImage;
    D4: TImage;
    E4: TImage;
    F4: TImage;
    G4: TImage;
    H4: TImage;
    D7: TImage;
    A5: TImage;
    B5: TImage;
    C5: TImage;
    D5: TImage;
    E5: TImage;
    F5: TImage;
    G5: TImage;
    H5: TImage;
    A6: TImage;
    B6: TImage;
    C7: TImage;
    C6: TImage;
    D6: TImage;
    E6: TImage;
    F6: TImage;
    G6: TImage;
    H6: TImage;
    A7: TImage;
    B7: TImage;
    H2: TImage;
    procedure A1Click(Sender: TObject);
    procedure A2Click(Sender: TObject);
    procedure A3Click(Sender: TObject);
    procedure A4Click(Sender: TObject);
    procedure A5Click(Sender: TObject);
    procedure A6Click(Sender: TObject);
    procedure A7Click(Sender: TObject);
    procedure A8Click(Sender: TObject);
    procedure B1Click(Sender: TObject);
    procedure B2Click(Sender: TObject);
    procedure B3Click(Sender: TObject);
    procedure B4Click(Sender: TObject);
    procedure B5Click(Sender: TObject);
    procedure B6Click(Sender: TObject);
    procedure B7Click(Sender: TObject);
    procedure B8Click(Sender: TObject);
    procedure C1Click(Sender: TObject);
    procedure C2Click(Sender: TObject);
    procedure C3Click(Sender: TObject);
    procedure C4Click(Sender: TObject);
    procedure C5Click(Sender: TObject);
    procedure C6Click(Sender: TObject);
    procedure C7Click(Sender: TObject);
    procedure C8Click(Sender: TObject);
    procedure D1Click(Sender: TObject);
    procedure D2Click(Sender: TObject);
    procedure D3Click(Sender: TObject);
    procedure D4Click(Sender: TObject);
    procedure D5Click(Sender: TObject);
    procedure D6Click(Sender: TObject);
    procedure D7Click(Sender: TObject);
    procedure D8Click(Sender: TObject);
    procedure E1Click(Sender: TObject);
    procedure E2Click(Sender: TObject);
    procedure E3Click(Sender: TObject);
    procedure E4Click(Sender: TObject);
    procedure E5Click(Sender: TObject);
    procedure E6Click(Sender: TObject);
    procedure E7Click(Sender: TObject);
    procedure E8Click(Sender: TObject);
    procedure F1Click(Sender: TObject);
    procedure F2Click(Sender: TObject);
    procedure F3Click(Sender: TObject);
    procedure F4Click(Sender: TObject);
    procedure F5Click(Sender: TObject);
    procedure F6Click(Sender: TObject);
    procedure F7Click(Sender: TObject);
    procedure F8Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure G1Click(Sender: TObject);
    procedure G2Click(Sender: TObject);
    procedure G3Click(Sender: TObject);
    procedure G4Click(Sender: TObject);
    procedure G5Click(Sender: TObject);
    procedure G6Click(Sender: TObject);
    procedure G7Click(Sender: TObject);
    procedure G8Click(Sender: TObject);
    procedure H1Click(Sender: TObject);
    procedure H2Click(Sender: TObject);
    procedure H3Click(Sender: TObject);
    procedure H4Click(Sender: TObject);
    procedure H5Click(Sender: TObject);
    procedure H6Click(Sender: TObject);
    procedure H7Click(Sender: TObject);
    procedure H8Click(Sender: TObject);
    procedure vyberpanaka(x,y:Integer);
    procedure posunpanaka(x,y:Integer);
    procedure presunpanaka(x,y:Integer);
  private
    { private declarations }
  public
    { public declarations }

  end;

var
  Form1: TForm1;
  a:array [1..8,1..8] of Integer;
  tah, ox, oy: Integer;
  rosada: Boolean;
//a - keeps track where units are. Its value is a 3-digit number, first digit signifying color, second type, third
//distinguishes between individual pieces (1-white, 2-black; 1-rook,2-tower,3-horse,4-bishop,5-king,
//6-queen) e.g - 216 - a black pawn (king and queen end with 0)
//tah - means "turn" 0,1-white, 2,3-black, 0,2-has not selected piece yet, 1,3-has selected a piece
//ox,oy - the current coordinates of the piece (x and y, the destinetion where the piece is to move, are
//used as local variables)
//rosada - means "castling"

implementation

uses
  Unit2;

{$R *.lfm}

{ TForm1 }

function pathcheck(x,y:integer):Boolean;
var
  i:integer;
begin
  Result:=False;
  //pawn
  if a[ox,oy] div 10=11 then begin
      if (ox=x)and(oy=7)and(y=oy-2)and(a[x,y]=0)and(a[x+1,y+1]=0)
          then Result:=True;
      if (ox=x)and(a[x,y]=0)and(y=oy-1) then Result:=True;
      if ((x=ox-1)or(x=ox+1))and(y=oy-1)and(a[x,y]>200) then Result:=True;
     end;
  if a[ox,oy] div 10=21 then begin
      if (ox=x)and(oy=2)and(y=oy+2)and(a[x,y]=0)and(a[x-1,y-1]=0)
          then Result:=True;
      if (ox=x)and(a[x,y]=0)and(y=oy+1) then Result:=True;
      if ((x=ox-1)or(x=ox+1))and(y=oy+1)and(a[x,y]div 100=1) then Result:=True;
     end;
  //tower
  if (((a[ox,oy] mod 100) div 10)=2) and ((ox=x)or(oy=y)) then begin
      Result:=True;
      if oy=y then begin
       if ox<x then for i:=ox+1 to x-1 do if a[i,y]>0 then Result:=False;
       if ox>x then for i:=x+1 to ox-1 do if a[i,y]>0 then Result:=False;
                   end;
      if ox=x then begin
       if oy<y then for i:=oy+1 to y-1 do if a[x,i]>0 then Result:=False;
       if oy>y then for i:=y+1 to oy-1 do if a[x,i]>0 then Result:=False;
                   end;
     end;
  //horse
  if (((a[ox,oy] mod 100) div 10)=3)and
     (((abs(ox-x)=2)and(abs(oy-y)=1))or((abs(oy-y)=2)and(abs(ox-x)=1)))
     then Result:=True;
  //bishop
  if (((a[ox,oy] mod 100) div 10)=4) and (abs(ox-x)=abs(oy-y)) then begin
      Result:=True;
      if (ox>x)and(oy>y) then for i:=x+1 to ox-1 do if a[i,oy-ox+i]>0
          then Result:=False;
      if (ox<x)and(oy>y) then for i:=ox+1 to x-1 do if a[i,oy-i+ox]>0
          then Result:=False;
      if (ox>x)and(oy<y) then for i:=ox-1 downto x+1 do if a[i,oy+ox-i]>0
          then Result:=False;
      if (ox<x)and(oy<y) then for i:=ox+1 to x-1 do if a[i,oy+i-ox]>0
          then Result:=False;
     end;
  //king
  if ((a[ox,oy] mod 100)=50)and((abs(x-ox)<=1)and(abs(y-oy)<=1))
      then Result:=True;
  //queen
  if (((a[ox,oy] mod 100) div 10)=6) and (abs(ox-x)=abs(oy-y)) then begin
      Result:=True;
      if (ox>x)and(oy>y) then for i:=x+1 to ox-1 do if a[i,oy-ox+i]>0
          then Result:=False;
      if (ox<x)and(oy>y) then for i:=ox+1 to x-1 do if a[i,oy-i+ox]>0
          then Result:=False;
      if (ox>x)and(oy<y) then for i:=ox-1 downto x+1 do if a[i,oy+ox-i]>0
          then Result:=False;
      if (ox<x)and(oy<y) then for i:=ox+1 to x-1 do if a[i,oy+i-ox]>0
          then Result:=False;
     end;
  if (((a[ox,oy] mod 100) div 10)=6) and ((ox=x)or(oy=y)) then begin
      Result:=True;
      if oy=y then begin
       if ox<x then for i:=ox+1 to x-1 do if a[i,y]>0 then Result:=False;
       if ox>x then for i:=x+1 to ox-1 do if a[i,y]>0 then Result:=False;
                   end;
      if ox=x then begin
       if oy<y then for i:=oy+1 to y-1 do if a[x,i]>0 then Result:=False;
       if oy>y then for i:=y+1 to oy-1 do if a[x,i]>0 then Result:=False;
                   end;
     end;
  //cant go to place occupied by friendly piece
  if ((a[x,y] div 100=1) and (tah=1)) or ((a[x,y] div 100=2) and (tah=3))
     then Result:=False;
  //castling (not exactly as it should be according to rules; a working PH script)
  if (((a[x,y]mod 100=21)or(a[x,y]mod 100=22))and(a[ox,oy]mod 100=50))or
     (((a[ox,oy]mod 100=21)or(a[ox,oy]mod 100=22))and(a[x,y]mod 100=50))
     and((ox=x)or(oy=y))and(a[x,y]div 100=a[ox,oy]div 100) then
     begin
      Result:=True;
      if oy=y then begin
       if ox<x then for i:=ox+1 to x-1 do if a[i,y]>0 then Result:=False;
       if ox>x then for i:=x+1 to ox-1 do if a[i,y]>0 then Result:=False;
                   end;
      if ox=x then begin
       if oy<y then for i:=oy+1 to y-1 do if a[x,i]>0 then Result:=False;
       if oy>y then for i:=y+1 to oy-1 do if a[x,i]>0 then Result:=False;
                   end;
      if Result then rosada:=True;
     end;
end;

procedure TForm1.vyberpanaka(x,y:Integer); //means "picking of a piece"
begin
  if ((tah=0) and (a[x,y]div 100=1))
  or ((tah=2) and (a[x,y]>200)) then begin
      sel.visible:=True;
      sel.left:=64*(x-1);
      sel.top:=64*(y-1);
      ox:=x;
      oy:=y;
      tah:=tah+1;
  end;
end;

procedure TForm1.posunpanaka(x,y:Integer); //means "move a piece"
begin
  //deselect if the original field is clicked again
  if (x=ox) and (y=oy) then begin sel.visible:=false; tah:=tah-1; end else
  if pathcheck(x,y) then presunpanaka(x,y);
end;

procedure TForm1.presunpanaka(x,y:Integer); //synonymous meaning with^
var
  p,r:Integer;
begin
  if a[x,y]=0 then p:=0 else p:=1;
  case a[ox,oy] of
    111:begin WP1.Left:=(x-1)*64; WP1.Top:=(y-1)*64; end;
    112:begin WP2.Left:=(x-1)*64; WP2.Top:=(y-1)*64; end;
    113:begin WP3.Left:=(x-1)*64; WP3.Top:=(y-1)*64; end;
    114:begin WP4.Left:=(x-1)*64; WP4.Top:=(y-1)*64; end;
    115:begin WP5.Left:=(x-1)*64; WP5.Top:=(y-1)*64; end;
    116:begin WP6.Left:=(x-1)*64; WP6.Top:=(y-1)*64; end;
    117:begin WP7.Left:=(x-1)*64; WP7.Top:=(y-1)*64; end;
    118:begin WP8.Left:=(x-1)*64; WP8.Top:=(y-1)*64; end;
    121:begin WT1.Left:=(x-1)*64; WT1.Top:=(y-1)*64; end;
    122:begin WT2.Left:=(x-1)*64; WT2.Top:=(y-1)*64; end;
    131:begin WH1.Left:=(x-1)*64; WH1.Top:=(y-1)*64; end;
    132:begin WH2.Left:=(x-1)*64; WH2.Top:=(y-1)*64; end;
    141:begin WB1.Left:=(x-1)*64; WB1.Top:=(y-1)*64; end;
    142:begin WB2.Left:=(x-1)*64; WB2.Top:=(y-1)*64; end;
    150:begin WK.Left:=(x-1)*64; WK.Top:=(y-1)*64; end;
    160:begin WQ.Left:=(x-1)*64; WQ.Top:=(y-1)*64; end;
    211:begin BP1.Left:=(x-1)*64; BP1.Top:=(y-1)*64; end;
    212:begin BP2.Left:=(x-1)*64; BP2.Top:=(y-1)*64; end;
    213:begin BP3.Left:=(x-1)*64; BP3.Top:=(y-1)*64; end;
    214:begin BP4.Left:=(x-1)*64; BP4.Top:=(y-1)*64; end;
    215:begin BP5.Left:=(x-1)*64; BP5.Top:=(y-1)*64; end;
    216:begin BP6.Left:=(x-1)*64; BP6.Top:=(y-1)*64; end;
    217:begin BP7.Left:=(x-1)*64; BP7.Top:=(y-1)*64; end;
    218:begin BP8.Left:=(x-1)*64; BP8.Top:=(y-1)*64; end;
    221:begin BT1.Left:=(x-1)*64; BT1.Top:=(y-1)*64; end;
    222:begin BT2.Left:=(x-1)*64; BT2.Top:=(y-1)*64; end;
    231:begin BH1.Left:=(x-1)*64; BH1.Top:=(y-1)*64; end;
    232:begin BH2.Left:=(x-1)*64; BH2.Top:=(y-1)*64; end;
    241:begin BB1.Left:=(x-1)*64; BB1.Top:=(y-1)*64; end;
    242:begin BB2.Left:=(x-1)*64; BB2.Top:=(y-1)*64; end;
    250:begin BK.Left:=(x-1)*64; BK.Top:=(y-1)*64; end;
    260:begin BQ.Left:=(x-1)*64; BQ.Top:=(y-1)*64; end;
  end;
  //eliminating
  if (p=1)and(not rosada) then
  case a[x,y] of
    111:WP1.Visible:=False;
    112:WP2.Visible:=False;
    113:WP3.Visible:=False;
    114:WP4.Visible:=False;
    115:WP5.Visible:=False;
    116:WP6.Visible:=False;
    117:WP7.Visible:=False;
    118:WP8.Visible:=False;
    121:WT1.Visible:=False;
    122:WT2.Visible:=False;
    131:WH1.Visible:=False;
    132:WH2.Visible:=False;
    141:WB1.Visible:=False;
    142:WB2.Visible:=False;
    150:WK.Visible:=False;
    160:WQ.Visible:=False;
    211:BP1.Visible:=False;
    212:BP2.Visible:=False;
    213:BP3.Visible:=False;
    214:BP4.Visible:=False;
    215:BP5.Visible:=False;
    216:BP6.Visible:=False;
    217:BP7.Visible:=False;
    218:BP8.Visible:=False;
    221:BT1.Visible:=False;
    222:BT2.Visible:=False;
    231:BH1.Visible:=False;
    232:BH2.Visible:=False;
    241:BB1.Visible:=False;
    242:BB2.Visible:=False;
    250:BK.Visible:=False;
    260:BQ.Visible:=False;
  end;
  if rosada then
//again PH, I know it is not supposed to work like this
  case a[x,y] of
    121:begin WT1.Left:=(ox-1)*64; WT1.Top:=(oy-1)*64; WK.Top:=(y-1)*64;
              WK.Left:=(x-1)*64 end;
    122:begin WT2.Left:=(ox-1)*64; WT2.Top:=(oy-1)*64; WK.Top:=(y-1)*64;
              WK.Left:=(x-1)*64 end;
    150:begin WK.Left:=(ox-1)*64; WK.Top:=(oy-1)*64;
              if a[ox,oy]=121 then begin WT1.Top:=(y-1)*64;
                                         WT1.Left:=(x-1)*64 end;
              if a[ox,oy]=122 then begin WT2.Top:=(y-1)*64;
                                         WT2.Left:=(x-1)*64 end;
              end;
    221:begin BT1.Left:=(ox-1)*64; BT1.Top:=(oy-1)*64; BK.Top:=(y-1)*64;
              BK.Left:=(x-1)*64 end;
    222:begin BT2.Left:=(ox-1)*64; BT2.Top:=(oy-1)*64; BK.Top:=(y-1)*64;
              BK.Left:=(x-1)*64 end;
    250:begin BK.Left:=(ox-1)*64; BK.Top:=(oy-1)*64;
              if a[ox,oy]=121 then begin BT1.Top:=(y-1)*64;
                                         BT1.Left:=(x-1)*64 end;
              if a[ox,oy]=122 then begin BT2.Top:=(y-1)*64;
                                         BT2.Left:=(x-1)*64 end;
              end;
  end;
  sel.visible:=False;
//Form2 shows here for testing purposes, it is not used for anything yet, but the placement is where it
//should be
  Form2.Showmodal;
  //resolve the new arrangment of pieces and turns
  if rosada then r:=a[x,y];
  a[x,y]:=a[ox,oy];
  if rosada then begin a[ox,oy]:=r; Rosada:=False; end else a[ox,oy]:=0;
  if tah=3 then tah:=0; if tah=1 then tah:=2;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
i,j:Integer;
begin
  rosada:=False;
  //drawing the board
  for i:=0 to 7 do for j:=0 to 7 do begin
   if ((i+j) mod 2=1) then Image1.Canvas.Brush.Color:=clBlack else
      Image1.Canvas.Brush.Color:=clWhite;
   Image1.Canvas.FillRect(i*64,j*64,(i+1)*64,(j+1)*64);
                                    end;
  //filling the array with the pieces' initial positions
  for i:=1 to 8 do a[i,2]:=210+i;
  for i:=1 to 8 do a[i,7]:=110+i;
  a[1,1]:=221;a[2,1]:=231;a[3,1]:=241;a[4,1]:=260;a[5,1]:=250;a[6,1]:=242;
  a[7,1]:=232;a[8,1]:=222;a[1,8]:=121;a[2,8]:=131;a[3,8]:=141;a[4,8]:=160;
  a[5,8]:=150;a[6,8]:=142;a[7,8]:=132;a[8,8]:=122;
  for i:=3 to 6 do for j:=1 to 8 do a[j,i]:=0;
  //the white starts
  tah:=0;
end;

//on-click actions of the fields follow, 64 identical procedures, with different parameters (only showing one for character limit)
procedure TForm1.G1Click(Sender: TObject);
begin
  if (tah=0) or (tah=2) then vyberpanaka(7,1) else posunpanaka(7,1);
end;
end.

Form2:
(for now just show pieces in the color of whatever player made the move, is supposed to be used for transforming pawns once they reach the end; currently always shows white ones, unless I assign values to ox and oy in the Form1.Formcreate as said before - then it can also show black, but again, will continue showing the same every time)

Code: [Select]

unit Unit2;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ExtCtrls;

type

  { TForm2 }

  TForm2 = class(TForm)
    Image1: TImage;
    Image2: TImage;
    Image3: TImage;
    Image4: TImage;
    procedure FormCreate(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end;

var
  Form2: TForm2;

implementation

uses
  Unit1;

{$R *.lfm}

{ TForm2 }

procedure TForm2.FormCreate(Sender: TObject);
begin
  if a[ox,oy]>200 then begin
    Image1.Picture.LoadFromFile('figurky/cierna_dama.png');
    Image2.Picture.LoadFromFile('figurky/cierna_veza.png');
    Image3.Picture.LoadFromFile('figurky/cierny_strelec.png');
    Image4.Picture.LoadFromFile('figurky/cierny_kon.png');
  end else begin
    Image1.Picture.LoadFromFile('figurky/biela_dama.png');
    Image2.Picture.LoadFromFile('figurky/biela_veza.png');
    Image3.Picture.LoadFromFile('figurky/biely_strelec.png');
    Image4.Picture.LoadFromFile('figurky/biely_kon.png');
  end;
end;

end.


[Never]

Did you try to use the code you post?!!!
i'm willing to help you
upload a zip file with a working example tha reproduces the error

[Bul the noob]

Yes, and it's working just fine (except for that one thing I this topic is about)
Here is it: http://www.filedropper.com/v2_1 (comments are in my language, for reference you can use the translations I posted here)

[Never]

there are missing images ....from your zip

you have set the form2 to be auto created

in order to get values ox,oy user interaction reguired

and thats y you don't get any values

form2 should be created and destroyed as required
or change the code to be exacute for ex: in onshow event
this will work can't test thought for the missing images

Code: [Select]


procedure TForm2.FormShow(Sender: TObject);
begin   
 ShowMessage(IntToStr(ox)+' - - '+IntToStr(oy));
  if a[ox,oy]>200 then begin
    Image1.Picture.LoadFromFile('figurky/cierna_dama.png');
    Image2.Picture.LoadFromFile('figurky/cierna_veza.png');
    Image3.Picture.LoadFromFile('figurky/cierny_strelec.png');
    Image4.Picture.LoadFromFile('figurky/cierny_kon.png');
  end else begin
    Image1.Picture.LoadFromFile('figurky/biela_dama.png');
    Image2.Picture.LoadFromFile('figurky/biela_veza.png');
    Image3.Picture.LoadFromFile('figurky/biely_strelec.png');
    Image4.Picture.LoadFromFile('figurky/biely_kon.png');
  end;
end;


[Bul the noob]

Sorry about forgetting to include the images. And thank you, it works!

[Never]

you are wellcome
good luck with your game