Question

I have two TEdit boxes that I am using to specify file paths, one is for UNC paths, the other is for a local path. However, I would like it so if the user can only enter text in one box. If they enter text in one box, it should clear the other one. How should I go about doing this? Also, not sure if I should use an OnEnter, OnChange, or some other method.

Answer 1

You can do it pretty simply. Create one OnChange handler, and assign it to both TEdits using the Object Inspector’s Events tab. Then you can use something like the following:

procedure TForm1.EditChanged(Sender: TObject); //Sender is the edit being changed
begin
  if Sender = UNCEdit then  // If it's is the UNCEdit being changed
  begin
    LocalPathEdit.OnChange := nil;            // Prevent recursive calling!
    LocalPathEdit.Text := '';                 // Clear the text
    LocalPathEdit.OnChange := EditChanged;    // Restore the event handler
  end;
  else
  begin
    UNCEdit.OnChange := nil;
    UNCEdit.Text := '';
    UNCEdit.OnChange := EditChanged;
  end;
end;

This can be streamlined slightly, but it’s not quite as readable to others. It can also be protected with a try..finally, although for simply clearing an edit’s text content it’s not really needed.

procedure TForm1.EditChanged(Sender: TObject);
var
  TmpEdit: TEdit;
begin
  if Sender = UNCEdit then
    TmpEdit := LocalPathEdit
  else
    TmpEdit := UNCEdit;
  TmpEdit.OnChange := nil;
  try
    TmpEdit.Text := '';
  finally
    TmpEdit.OnChange := EditChanged;
  end;
end;