Delphi program suddenly won't post query changes

Question

I have Delphi application that has been in production for several years now and recently a specific piece of code has stopped working. In the OnClose event for the form I have the following:

procedure TfrmPublicEmpInfo.FormClose(Sender: TObject;var Action: TCloseAction);  
var
  i : integer;  
  strWorkDays : string;  
begin  
  If cbMonday.Checked then strWorkDays := strWorkDays + 'Mo';  
  If cbTuesday.Checked then strWorkdays := strWorkDays + 'Tu';  
  If cbWednesday.Checked then strWorkdays := strWorkDays + 'We';  
  If cbThursday.Checked then strWorkdays := strWorkDays + 'Th';  
  If cbFriday.Checked then strWorkdays := strWorkDays + 'Fr';  
  If cbSaturday.Checked then strWorkdays := strWorkDays + 'Sa';  
  If cbSunday.Checked then strWorkdays := strWorkDays + 'Su';  
  if strWorkDays <> '' then    
  begin  
    qryPubEmployees.Edit;  
    qryPubEmployees.FieldValues['OCCUPATION'] := strWorkDays;  
  end;  

  dtpPEEndTimeChange(self);   
  dtpPEStartTimeChange(self);  

  For i := 0 to ComponentCount - 1 do  
  begin  
    If Components[i] is TQuery Then  
      with Components[i] as TQuery do  
      begin  
        if State = dsEdit then  
        post;  
      end;  
  end;  
end;

It gets to the dtpPEEndTimeChange(self) call which is this:

procedure TfrmPublicEmpInfo.dtpPEEndTimeChange(Sender: TObject);  
begin  
  qryPubEmployees.Edit;  
  dbePEEndTime.Field.Value := StrToInt(FormatDateTime('HHMM', dtpPEEndTime.Time));  
end;  

while in this function the program calls Windows.pas and gets stuck in:

function GetTickCount; external kernel32 name 'GetTickCount';

it never posts the changes to the record.

Does anyone know if any Windows updates may have caused this malfunction? We are currently on Windows XP Professional Version 5.1 SP 3.

Answer 1

GetTickCount returns Cardinal. If you are storing result to integer variable, it will result to integer overflow when your computer has been up for 25 days or so. I'm just guessing, but that once was problem in our application.

Answer 2

Your code sends off alarm bells in my head.

Unrelated to your problem, I consider it very bad style to have directly executed code in my FormClose event that can cause a chain of other activity. In other words, good style would be that FormClose calls a "PostChanges" procedure, that validates and then posts data.

I also wonder why you have written a For Loop to search your form for TQuery typed objects and call post merely because they are in an Edit state. Shouldn't there be some validation logic?

Secondly, your "OnChange" events are tricky. Almost all OnChange events require code like this:

procedure TfrmPublicEmpInfo.dtpPEEndTimeChange(Sender: TObject);  
begin  
  if FUpdating then exit;  // safety!
  qryPubEmployees.Edit;  
  FUpdating := true; // this part might not be necessary, but you should try it and see if it is, somehow.
  try 
    dbePEEndTime.Field.Value := StrToInt(FormatDateTime('HHMM', dtpPEEndTime.Time));  
  finally
       FUpdating := false;
  end;
end;  

Then you have to set FUpdating to true in your FormClose event, and clear it at the end of FormClose, and prevent extra calls to this event from messing you up. Remember that OnChange gets called NOT ONLY when you type something, but also when you assign dtpPEEndTime.Field.Value by code, so you can get an endless recursion.