Delphi beginner - using loop with TEdit

Question

I have 10 TEdits and 10 images and I tried to use this:

procedure TForm1.Button1Click(Sender: TObject; edit: TEdit);
var i:integer;
begin
for i:= 1 to 10 do
  begin
   if edit[i].text:='1' then picture[i].Show else picture[i].Hide;
  end;
end;

But delphi returns this error: [Error] Unit1.pas(84): Class does not have a default property

I also tried this:

procedure TForm1.Button1Click(Sender: TObject);
var i:integer;
begin
for i:= 1 to 10 do
  begin
   if edit[i].text:='1' then picture[i].Show else picture[i].Hide;
  end;
end;

But, again, Delphi returns errors:

[Error] Unit1.pas(84): Undeclared identifier: 'edit'.

Can you help me with this code?

Lots of fundamental errors here. := is the assignment operator, = is comparison. Be sure not to confuse these. It seems you have not declared any arrays named edit or picture. If you want to access your controls in an array you need to declare those arrays and then place references to the controls in them. Also note that you cannot change the method signature of a TNotifyEvent - it must have only one parameter (Sender : TObject). — J...
– J..., Commented Nov 5, 2015 at 18:06
See also: Forming a variable name with string + integer and calling functions How can I refer to a control whose name is determined at runtime? How to create an array of controls? — Rob Kennedy
– Rob Kennedy, Commented Nov 5, 2015 at 20:43

Remy Lebeau · Accepted Answer · 2015-11-05 18:06:49Z

You need to declare and populate your own arrays, and then you can loop through them when needed, eg:

type
  TForm1 = class(TForm)
    Button1: TButton;
    ...
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    // and so on ...
    Image1: TImage;
    Image2: TImage;
    Image3: TImage;
    // and so on ...
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    ...
  private
    edit: array[1..10] of TEdit;
    picture: array[1..10] of TImage;
    ...
  end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  edit[1] := Edit1;
  edit[2] := Edit2;
  edit[3] := Edit3;
  // and so on...
  picture[1] := Image1;
  picture[2] := Image2;
  picture[3] := Image3;
  // and so on...

  {
  alternatively:

  for I := 1 to 10 do
  begin
    edit[i] := TEdit(FindComponent('Edit' + IntToStr(i)));
    picture[i] := TImage(FindComponent('Image' + IntToStr(i)));
  end;
  }
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  I: integer;
begin
  for I := 1 to 10 do
  begin
   if edit[i].Text = '1' then
     picture[i].Show
   else
     picture[i].Hide;
   {
   alternatively:
   picture[i].Visible := (edit[i].Text = '1');
   }
  end;
end;

Ken White · Accepted Answer · 2015-11-05 18:37:15Z

You can do one of two things:

Use the form's Components list and FindComponent:

procedure TForm1.Button1Click(Sender: TObject);
var 
  i: Integer;
  TempEdit: TEdit;
begin
  for i:= 1 to 10 do
  begin
    TempEdit := Self.FindComponent('Edit' + IntToStr[i]) as TEdit;
    if Assigned(TempEdit) then
    begin
      if TempEdit.Text = '1' then
        Picture[i].Show
      else
        Picture[i].Hide;
    end;
  end;
end;

Maintain a separate array of your TEdit controls, and reference them directly. When you assign Picture[i], add the matching TEdit to Edits[i], and then

procedure TForm1.Button1Click(Sender: TObject);
var 
  i: Integer;
begin
  for i:= 1 to 10 do
  begin
    if Edits[i].Text = '1' then
        Picture[i].Show
      else
        Picture[i].Hide;
    end;
  end;
end;

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