Use variables for object name in Delphi

Question

I'm trying to change the caption of many labels using regular way:

form1.label1.caption := '1';
form1.label2.caption := '2';
form1.label3.caption := '3';
form1.label4.caption := '4';
form1.label5.caption := '5';
form1.label6.caption := '6';
form1.label7.caption := '7';
form1.label8.caption := '8';
...

How can I use For and assign i to label name like Label[i]? Something like this:

for i := 1 to 50 do
   begin
     form1.label[i].caption := Inttostr(i);
   end;

And what is the best way to change too many object parameters (In this case caption)?

Take a look here stackoverflow.com/questions/16710189/…. Or just use Findcomponent to search the site. — bummi
– bummi, Commented Sep 15, 2013 at 13:38
Thanks @bummi for the question, but I did not suggest to use it, but to use it for search, since this has been asked often before in different colors and questions containing FindComponent show different solutions besides to FindComponent. Since I know it's sometimes difficult without the keyword to find existing solutions I decided not to search for a exact duplicate for closing. — bummi
– bummi, Commented Sep 15, 2013 at 16:10

Arkady · Accepted Answer · 2019-11-14 13:42:34Z

14

If you are sure you have 50 labels label1, label2 .. label50
The solution could be like this:

var lbl: TLabel;
for i:=1 to 50 do
begin
    lbl := FindComponent('Label'+IntToStr(i)) as TLabel;
    lbl.Caption := IntToStr(i);
end;

edited Nov 14, 2019 at 13:42

answered Sep 15, 2013 at 14:43

Arkady

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5 Comments

Sky Over a year ago

@AndreasRejbrand Why you don't like this? What's wrong with this?

Andreas Rejbrand Over a year ago

A numebr of things. For one thing, FindComponent takes some time to compute; you need to compare a lot of strings. This you don't have to do if you use arrays. Second, using arrays you get 100 % control over the life of the controls. You can create them dynamically, change them dynamically, and remove them dynamically.

David Heffernan Over a year ago

FindComponent binds to the control at runtime. If you can bind at compile time then the compiler can check correctness. If you change the name of the components, you only discover FindComponent failures at runtime. Always prefer compile time solutions to runtime solutions. If there are no compile time solutions, use runtime solution. Otherwise, prefer compile time.

Free Consulting Over a year ago

FindComponent is unlikely to become a bottleneck.

David Heffernan Over a year ago

@Free Agreed. Not a bottleneck. More about aesthetics, style maintainability etc.

David Heffernan · Accepted Answer · 2013-09-15 13:40:52Z

9

Create your controls dynamically. If you need to retain references to them hold those references in an array. For example, this is the general pattern.

var
  FLabels: array of TLabel;
....
SetLength(FLabels, Count);
for i := 0 to Count-1 do
begin
  FLabels[i] := TLabel.Create(Self);
  FLabels[i].Parent := Self;
  FLabels[i].Caption := IntToStr(i+1);
  FLabels[i].Left := 8;
  FLabels[i].Top := 8 + i*20;
end;

answered Sep 15, 2013 at 13:40

David Heffernan

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1 Comment

Sky Over a year ago

Thanks. Nice code. Can I use this in threads? I mean is this Thread-safe?

Harriv · Accepted Answer · 2013-09-15 14:48:26Z

3

If you want to change all labels on the form, you can use something like this:

for i := 0 to Form1.ComponentCount do
  if Form1.Components[i] is TLabel then
    TLabel(Form1.Components[i]).Caption := IntToStr(i + 1);

If labels are on Panel or some other container, you can limit this by replacing Form1 by eg "Form1.Panel1". You can also use eg. the tag property of components to easily select which labels you want to change.

answered Sep 15, 2013 at 14:48

Harriv

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