How do I prevent the user from clicking a button too often? - delphi

Question

In a button-click event, I am sending a command to a server. I don't want the server to be flooded with requests, so I want to prevent the user from clicking the button too often.
I've thought about counting how many times the button is clicked, like this:
button.tag := button.tag + 1;
if button.Tag = 5 then
exit;
But this will not help because I have to set the tag to 0 each time I need to detect the fast clicks, and this will also not help because it will detect the tag number every 5 clicks, whereas I just need to know if the button was clicked repeatedly.
How do I detect fast button clicks without using the button tag?

Answer 1

If you want to restrict how often to send commands from your client to the server, disable the button a short while after each click. This will give the user feedback that something is processing. I'm assuming there is no way the server can give feedback when it is ready.
procedure TForm1.Button1Click(Sender: TObject);
begin
Button1.Enabled := false;
Timer1.Interval := 500; // Pick a suitable interval
Timer1.Enabled := true;
SendCommand(); // Make call to server
end;
procedure TForm1.Timer1Timer(Sender: TObject);
// Timer1 is disabled at startup
begin
Button1.Enabled := true;
Timer1.Enabled := false;
end;
Note: if you are trying to do some load balancing on the server, there must be a way for the clients to know how to restrict the calls. But this is all a backwards way of doing it, the server should be capable of handling this without any restrictions on the clients.

Answer 2

You've correctly recognized that merely counting the clicks won't be sufficient. You need to account for the time, too. So use a timer.
When the button is clicked, disable the button and enable a timer. When the timer fires, re-enable the button.
procedure TExampleForm.SendButtonClick(Sender: TObject);
begin
Assert(SendButton = Sender);
SendButton.Enabled := False;
SendButtonTimer.Enabled := True;
SendCommandToServer(...);
end;
procedure TExampleForm.SendButtonTimerTimer(Sender: TObject);
begin
Assert(SendButtonTimer = Sender);
SendButtonTimer.Enabled := False;
SendButton.Enabled := True;
end;
Set the timer's Interval property to the number of milliseconds that you want the button to remain disabled.
There's no need to count the clicks in this scenario because the implicit limit is one click per timer interval.

Answer 3

You could just put some kind of timestamp into the Tag, and check whether enough time has elapsed.
Better yet, derive your own class, (TDontPressMeTooFastButton ;-), and you can do whatever you want, ie.:
track both how much time elapsed since last click and how many "fast clicks" the user attempted
you could make the button contain the timer component, not leaking this implementation detail into the form
Just about anything, in a much cleaner way than using the .Tag or global/form variables ...