Hi,
Can anyone give me an example of adding and retrieving an integer value to a TTreenode via it's data property please?

I've tried the below, but it doesn't seem to work.

Set:
with
tvMain.Items.AddChildObject(tvMain.Selected,'string',TObject(fUserList.Items[I].Id)) do

and getting as, throws an exception on start:
procedure TfrmMain.tvMainChange(Sender: TObject; Node: TTreeNode);
begin
  ShowMessage('Node ' + IntToStr(Integer(Node.Data)));
end;

Thanks in advance

Richard
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Le 11/09/2013 07:51, Richard Mace a ?crit :

change to:
with tvMain.Items.AddChildObject(tvMain.Selected,'string', *Pointer*(fUserList.Items[I].Id)) do

change to:
ShowMessage('Node ' + IntToStr(*PtrInt***(Node.Data)));

Antonio.

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Also unless you want the treeview to behave as if it were fully initialised with Data integer values of zero, you would need to add:

procedure TfrmMain.tvMainChange(Sender: TObject; Node: TTreeNode);
begin
   if Assigned(Node) then
     ShowMessage('Node ' + IntToStr(PtrInt(Node.Data)));

Richard Mace wrote

Can anyone give me an example of adding and retrieving an integer value to a TTreenode via it's data property please?

The Data property holds a pointer value, so don't assign an Integer directly. Rather define a Record structure (or a Class) that holds the data you want (in your case an Integer field), then assign the pointer to the record structure to the Treenode.Data property.

There is an example in the LCL documentation:

http://lazarus-ccr.sourceforge.net/docs/lcl/comctrls/ttreenode.data.html

Regards,
Graeme

Thanks for the reply.
Can't it be type casted because both a pointer and integer are 4 bytes?

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Richard Mace wrote

Can't it be type casted because both a pointer and integer are 4 bytes?

They are both 4 bytes only in 32-bit computers.

Juha

Thanks for the reply. Can't it be type casted because both a pointer and integer are 4 bytes?

Dunno about Lazarus, but casts work in Delphi.

Hint: pointers may be longer than integers, but never shorter. So you won't loose information when e.g. storing an 32 bit integer into a 64 bit pointer field. Consequently the opposite direction, i.e. storing an pointer in an integer field, may not work.

That's why newer Delphi versions also have the Tag properties expanded, so that it's possible to store pointers there.

DoDi

I'd store fUserList.Items[I] there, which is an address and allows access to further values later.

DoDi

Juha Manninen wrote

They are both 4 bytes only in 32-bit computers.

+1

Regards,
- Graeme -

And if your program is compiled to 32bit executable and ran on 64bit mode Windows in compat mode (e.g. win7+)?

(i guess this question is rhetorical ;)

-L.

I guess you mean "if Assigned(Node.Data) then" ?

-Fl?vio

Indeed that is what I meant, not what I wrote!

In this case you can omit the "if" entirely.

DoDi

I don't agree this is a rule of thumb. If you know what you're doing you should store whatever data fits in Data (pointer size) and avoid the hundreds of tiny annoying allocations...

Regards,
Fl?vio

OK, thanks for everyone's input. I have re-written it with the following, but ShowMessage still isn't display the correct User.Id For clarification fUserList is a TObjectList

with tvMain.Items.AddChild(tvMain.Selected,IntToStr(fUserList.Items[I].Id))
do
  begin
    Data := fUserList.Items[I];
    ImageIndex := 2;
  end;
procedure TfrmMain.tvMainSelectionChanged(Sender: TObject);
begin
  if Assigned(TTreeNode(Sender).Data) then
    ShowMessage('Node ' + IntToStr(TUser(TTreeNode(Sender).Data).Id));
end;

I'm obviously doing something a bit daft, but can't work out what? Any input would be greatly received.

Thanks

Richard
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[...] procedure TfrmMain.tvMainSelectionChanged(Sender: TObject); begin

Sender is the tvMain.

Mattias

OK, I now have this code:
with
tvMain.Items.AddChildObject(tvMain.Selected,IntToStr(fUserList.Items[I].Id),Pointer(fUserList.Items[I].Id)) do

and this:
procedure TfrmMain.tvMainChange(Sender: TObject; Node: TTreeNode);
begin
  if Assigned(Node.Data) then
    ShowMessage('Node ' + IntToStr(PtrInt(Node.Data)));
end;

And I am now getting an exception when my app run?

Richard

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Richard Mace wrote

And I am now getting an exception when my app run?

Use debugger to see what goes wrong.

Juha

Le 13/09/2013 07:48, Richard Mace a ?crit :

Details are missing about your implementation: Lzarus & FPC, OS, etc. I've made a little test on Win32 and Linux_X64, Lazarus 1.0.12 I added some nodes to the TTreeView like this:

var
   SData: Integer=179;
procedure TFrmMain.BtnTestTvClick(Sender: TObject);
var
   wNode: TTreeNode = nil;
   s: String;
begin
   Inc(SData);
   wNode := Ttv.Items.AddChildObject(nil, 'node new', Pointer(SData));
   s := Format('node %s data:%d', [wNode.Text, PtrInt(wNode.Data)]);
   MessageDlg('Titre', s, mtInformation, [mbOK], 0, mbOK);
end;
The I added an event to Ttv.OnChange event like that:
procedure TFrmMain.TtvChange(Sender: TObject; Node: TTreeNode);
var
   wData: Integer;
begin
   if Assigned(Node) then begin
     wData := PtrInt(Node.Data);
     MessageDlg('Titre',Format('data for "%s" %d', [Node.Text, wData]),
mtInformation, [mbOK], 0, mbOK);
   end;
end;

I get a new node on every BtnTestTvClick and a value starting from 180 on every OnChange event
On both platforms.

Antonio.

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Antonio Fortuny wrote

Le 13/09/2013 07:48, Richard Mace a ?crit : > OK, I now have this code: Details are missing about your implementation: Lzarus & FPC, OS, etc.

Guessing Windows x86 - not writing a FreeSwitch control application, by any chance [1] ;)

http://thread.gmane.org/gmane.comp.telephony.freeswitch.user/64508

It is, and yes I am. :-)

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Nice. Use FS a bit myself - nice to see Lazarus tooling for it appear.

Thanks Antonio, that worked fine.
Goodness knows what I was originally doing!

Richard

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Le 17/09/2013 07:16, Richard Mace a ?crit :

Thanks Antonio, that worked fine. Goodness knows what I was originally doing!

Nothing less I did when I started to play with pointers. 8-) Happy to be usefull.

Antonio.

Richard

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