Is it possible to access a TButton using tag?

Question

I hope to access a TButton using tag. IS it possible?

for example, I hope set the caption of a TButton (button1 has tag 3) as 'aaa', I know I can use

button1.caption:='aaa';

but I hope to use tag '3' to access the tbutton and set the string value 'aaa'.

Welcome any comment

Thanks

interdev

You are going to have be a bit more explicit as to what it is you want to do. — Nick Hodges, Dec 22 '10 at 14:41
@user262325 - will you have the tags unique or you want to set the caption for more than one component (have the same Tag for more buttons) ? — , Dec 22 '10 at 15:10

score 5 · Accepted Answer · answered Dec 22 '10 at 14:53

5

procedure TForm1.ChnCaptionByTag(SearchTag: integer; NewCpt: string);
var
  i: Integer;
begin
  for i := 0 to ComponentCount - 1 do
    if Components[i] is TButton then
    begin
      if TButton(Components[i]).Tag = SearchTag then
         TButton(Components[i]).Caption := NewCpt;
    end;
end;

answered Dec 22 '10 at 14:53

SimaWB

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Maaan I always get late. I was giving the same answer. Also tags among the buttons must be unique, otherwise,you have the last button with the spesified tag. – ali_bahoo Dec 22 '10 at 14:56
sorry, taking back, what about Break; from the loop – Dec 22 '10 at 14:58
@daemon: if user262325 has multiple buttons with the same tag? – SimaWB Dec 22 '10 at 15:02

score 2 · Answer 2 · answered Dec 22 '10 at 14:55

2

There is no direct way to do

 ButtonByTag(3).Caption := 'aaa';

You can search through a form's components looking for something with a tag of 3:

 var C: TComponent;

 for C in Self.Components do
    if C is TCustomButton then
      if C.Tag = 3 then
        (C as TCustomButton).Caption := 'aaa'

But note that you could have plenty of components with the same tag, it's not guaranteed unique.

answered Dec 22 '10 at 14:55

Larry Lustig

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Nice - I never knew about the "for C in self.components"; I always did the "for i:=0 to ControlCount (or componentcount)" – M Schenkel Dec 22 '10 at 14:59
1

what about Break; from the loop ? – Dec 22 '10 at 14:59
@M Schenkel - it's since D2005 – Dec 22 '10 at 15:01
@daemon_x: I assume that the OP wants ALL buttons with tag 3. If he only wants the first one then yes, break is the way to go. – Larry Lustig Dec 22 '10 at 15:19
@Larry Lustig - who knows ? he's probably satisfied with the answer, so this will be maybe the next not accepted solution :( – Dec 22 '10 at 15:25
@Larry Lustig - +1 for you (for-in) – Dec 22 '10 at 15:27
@user: Both are answers are pretty much the same, so SimaWBs should take precedence. – Larry Lustig Dec 22 '10 at 15:47

score 2 · Answer 3 · answered Dec 22 '10 at 14:57

2

I think this should work:

procedure TForm1.SetCaption(iTag: Integer; mCaption: String);
var
  i: Integer;
begin
  for i:= 0 to controlcount-1 do
    if controls[i] is TButton then
      if TButton(controls[i]).Tag = iTag then
        TButton(controls[i]).Caption := mCaption;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  SetCaption(3,'aaa');
end;

answered Dec 22 '10 at 14:57

M Schenkel

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what about Break; from the loop ? – Dec 22 '10 at 15:01
1

The original question didn't specify whether multiple buttons might share the same tag... An early _break_ might be wrong. – Paul-Jan Dec 22 '10 at 15:04
+1 for you argument. I wanted also some points, because of the ads reduction :P – Dec 22 '10 at 15:13
to be a stickler, you can give to the parameters "const" type :) – Dec 22 '10 at 15:14

score 1 · Answer 4 · edited May 23 '17 at 11:50

1

Well, right now the Tag property is the same size as a Pointer, so you could, but you need to describe a bit more of what it is you'd like to do.

I'm not positive that this is going to continue to be the case moving into 64-bit Delphi, but I think that's the case too.

Edit: Yes, TComponent.Tag should be a NativeInt in future versions. References: Barry Kelly, Alexandru Ciobanu

edited May 23 '17 at 11:50

Community

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answered Dec 22 '10 at 14:35

afrazier

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In a conference in Brazil this year, David I. said that next year there will be a 64 bit and MAC compiler -- The Tag property will be a 64 big integer if code is compiled for 64 bit platform. – Dec 22 '10 at 14:39
mac compiler？ is it for apple's mac? – arachide Dec 22 '10 at 14:42
@user262325 - Yes, there's plans to make a Mac compiler for Delphi. See the [Roadmap](http://edn.embarcadero.com/article/39934) – afrazier Dec 22 '10 at 14:54

score 0 · Answer 5 · answered Dec 22 '10 at 15:06

procedure TForm1.ChangeCaptionByTag(const SearchTag: integer; const NewCaption: string);
var i: Integer;
begin
  for i in Components do
    if Components[i] is TButton then
      if (Components[i] as TButton).Tag = SearchTag then
        begin
          (Components[i] as TButton).Caption := NewCaption;
          Break;
        end;
end;

Is it possible to access a TButton using tag?

5 Answers5