Re: [Lazarus] how to get Type of Sender or Components[i] in order to Cast?

[Michael Van Canneyt]

On Mon, 27 Jul 2015, Mark Morgan Lloyd wrote:

JuuS wrote:

On 07/27/2015 09:31 AM, Mark Morgan Lloyd wrote:

Péter Gábor wrote:

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} ;

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.

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.
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