Thanks.
Bob B.

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If you typecast something you can use the fields and properties of the type you use for casting, for example:

if TCheckBox(Sender).Checked then {do_something}  ;

or

if TCheckBox(Components[I]).Checked then {do_something}  ;

2015-07-27 00:31 keltez?ssel, Bob B. ?rta:

Sorry!
I was "misreading" your mail... you want to know the type of them.

You can compare the type of them:

if Sender = TButton then { do something} ;

or you can get the name of the class

ShowMessage( Sender.classname );

2015-07-27 07:30 keltez?ssel, P?ter G?bor ?rta:

The correct operator is "is" not "=".

Regards,
Sven
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Can this be elegantly put into a case statement?

Hi, I just tried it and no you can't. At least not directly, there may be a way of casting the Sender object to ordinal or string but I'm not sure that is efficient or elegant.

Why not simply iterate the control List:

for i := 0 to Controls.Count - 1 do
begin
  If controls[ i ] is TCheckbox then
    TCheckbox( Controls[ i ] ).Checked := ....
end;

I didn't think there was, but thought it worth asking. My use case is this sort of thing:

         if MainForm.OutputComponent is TListBox then
           with MainForm.ListBox1 do begin
             Font.Name := fontName;
             Font.Size := fontSize
           end;
         if MainForm.OutputComponent is TMemo then
           with MainForm.Memo1 do begin
             Font.Name := fontName;
             Font.Size := fontSize
           end;
         ...

Now obviously I could have a separate property holding an enumeration, but it's a pity that it's not possible to do something like

         case MainForm.OutputComponent of
           TListBox: begin end;
           TMemo:    begin end;
           ...
         otherwise
           // Fatal exception since this is a serious programming error
         end;

You can:
   Case Lowercase(MainForm.OutputComponent.Classname) of
     'tlistbox' : begin end;
     'tmemo' : begin end;

Michael.

If you use the classname property you can:

case Sender.classname of
  'TCheckBox': ShowMessage('This is a TCheckBox');
end;

2015-07-27 09:31 keltez?ssel, Mark Morgan Lloyd ?rta:

Good point. I wonder if that's mode-specific (language manual simply says "Free Pascal allows").

P?ter G?bor wrote

if Sender = TButton then { do something} ;

I suppose you meant

if Sender is TButton then { do something} ;

OP: If you want to deal with a lot of different classes that might be the sender, it might help to define an array of these classes (types) and search it.

-Michael

If all you need to do is to change the Font you can also just use a cracker class or use a bogus unchecked to e.g. TMemo (accompanied by informative comments ;-) , since Font is declared in TControl.

Regards,
Fl?vio

2015-07-27 13:33 keltez?ssel, Michael Schnell ?rta:

Yes!

Am 27.07.2015 12:06 schrieb "Mark Morgan Lloyd" <

"Free Pascal allows").

I'm not aware that it is mode specific. But it will work only with FPC ;)

Regards,
Sven
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Am 27.07.2015 11:37 schrieb "Mark Morgan Lloyd" <

: Now obviously I could have a separate property holding an enumeration,

but it's a pity that it's not possible to do something like

I had already thought about a TClass-case myself, but the first problem is whether the case labels should be strict ("x.ClassType = y") or loose ("x is y") [for Strings and Ordinals that is no problem]. And if the latter, what if the type is a TEdit, but you have labels for example for TCustomEdit and TControl? Also ranges should probably not be allowed (e.g. TControl..TEdit).

Regards,
Sven
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