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Indirect addressing

Posted on 2009-05-13
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Last Modified: 2012-05-06
Hi Experts,
I have 20 edit boxes (ebxB01 .. ebxB20). Edit box ebxA contains a number between 1 .. 20. Based on this value I'd like to hide/show this edit boxes. For example ebxA.Text=5 in this case ebxB01 .. ebxB05 are visible and ebxB06 .. ebxB20 are hidden.
I don't want to to write 20 times this command. Would be possible to solve this job using a for ...next loop?
Every idea appreciated.
kind regards
Janos
0
Comment
Question by:kacor
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12 Comments
 
LVL 14

Expert Comment

by:SteveBay
ID: 24374584
You will want to start with a loop that looks something like this:
procedure TForm1.Button1Click(Sender: TObject);
var i : Integer;
begin
     for i := 0 to Form1.ControlCount - 1 do
          begin
          if (Form1.Controls[i] is TEdit) and
             pos('ebxB',TEdit(Form1.Controls[i]).Name)) > 0 then
               begin
               if TEdit(Form1.Controls[i]).Text = SomeValue then
                    begin
                    DoSomeThing;
                    end;
               end;
          end;
end;

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0
 
LVL 14

Expert Comment

by:SteveBay
ID: 24374683
A slighlty more detailed version:
procedure TForm1.Button1Click(Sender: TObject);
var  i : Integer;
     FieldNum : Integer;
begin
     for i := 0 to Form1.ControlCount - 1 do
          begin
          // establish that this is a TEdit
          // and that this is one with the correct name
          if (Form1.Controls[i] is TEdit) and
             pos('ebxB',TEdit(Form1.Controls[i]).Name)) > 0 then
               begin
               // extract the edit number from the name
               FieldNum := StrToIntDef(copy(Form1.Controls[i]),5,2),0);
               case FieldNum of
               1 : DoFunction01;
               2:  DoFunction02;
               //..
               //..
               20: DOFunciton20;
               else : DoFunctionDefault; //  StrToIntDef returned 0
                    end;//case
               end; // if
          end; // for
end;

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0
 
LVL 10

Author Comment

by:kacor
ID: 24374959
Hi SteveBay,
I tested the first offered solution with one button, two edit boxes and the following procedure

procedure TForm1.Button1Click(Sender: TObject);
var i : Integer;
begin
     for i := 0 to Form1.ControlCount - 1 do
          begin
          if (Form1.Controls[i] is TEdit) and
             pos('ebxB',TEdit(Form1.Controls[i]).Name)) > 0 then
               begin
                    Form1.Controls[i].Visible:=False;
               end;
          end;
end;

but I got an error message

[Error] Unit1.pas(34): Operator not applicable to this operand type

Janos
0
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LVL 10

Author Comment

by:kacor
ID: 24374972
the 34. line is:

             pos('ebxB',TEdit(Form1.Controls[i]).Name)) > 0 then
0
 
LVL 14

Expert Comment

by:SteveBay
ID: 24374995
should read :
IF pos('ebxB',TEdit(Form1.Controls[i]).Name)) > 0 then
0
 
LVL 10

Author Comment

by:kacor
ID: 24375032

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;
 
type
  TForm1 = class(TForm)
    Button1: TButton;
    ebxB2: TEdit;
    ebxB1: TEdit;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.Button1Click(Sender: TObject);
var i : Integer;
begin
     for i := 0 to Form1.ControlCount - 1 do
          begin
          if (Form1.Controls[i] is TEdit) and
             pos('ebxB',TEdit(Form1.Controls[i]).Name)) > 0 then
               begin
                    Form1.Controls[i].Visible:=False;
               end;
          end;
end;
 
end.

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0
 
LVL 6

Expert Comment

by:bokist
ID: 24375058
Better use component instead of control


   for i := 0 to Form1.ComponentCount - 1 do
      begin
      if  (Form1.Components[i] is TEdit) then
.....
0
 
LVL 37

Expert Comment

by:Geert Gruwez
ID: 24375070
you could also use Self instead of Form1

and you can also use FindComponent

for I := 1 to 20 do
begin
  edt := TEdit(FindComponent(Format('ebxB%2.2d', [I])));
  if Assigned(edt) and edt.Visible then
  begin
    ShowMessage(edt.Name + ' = ' + edt.Text);
  end;
end;
0
 
LVL 37

Expert Comment

by:Geert Gruwez
ID: 24375099
controlcount will not iterate the labels, so less iterations,
so better with controlcount instead of component ...
unless you have other non wincontrol components off course
0
 
LVL 14

Accepted Solution

by:
SteveBay earned 250 total points
ID: 24375152
Sorry about that. Itr should be :

          if (Form1.Controls[i] is TEdit) and
             (pos('ebxB',TEdit(Form1.Controls[i]).Name) > 0) then

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0
 
LVL 6

Assisted Solution

by:twocandles
twocandles earned 250 total points
ID: 24375400
Place all the related edits inside a container (panel, groupbox...) and loop through the container components instead of forms'.

Another approach

procedure TForm2.Button1Click(Sender: TObject);
const
    MAX_EDIT_BOXES = 2;
    EDIT_BOX_PREFIX = 'ebxB';
    EB_FORMAT = '%.2d';
var
    i, firstBox : integer;
    c : TComponent;
    s : string;
begin
    // Check edit contains a valid integer or give it a non useful value
    firstBox := StrToIntDef( edit1.Text, MAX_EDIT_BOXES + 1 );
    // Loop
    for i := firstBox to MAX_EDIT_BOXES do
    begin
        c := FindComponent( EDIT_BOX_PREFIX + Format( EB_FORMAT, [i] ) );
        if( c is TEdit )then
            TEdit( c ).Visible := false;
    end;
end;

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0
 
LVL 10

Author Closing Comment

by:kacor
ID: 31580956
Thank you guys for the excellent tips. I use both of them.
Janos
0

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