Why is EOF ignored in this code? 3

[delphiman]

Can somone please throw some light on this?

The ShowMessage proves that the routine
progresses through the TQuery - but then stops on
the last record. Ignoring the EOF. Why?

procedure TfrmThisForm.btn1Click(Sender: TObject);
var
ABookmark : TBookmark;
begin
with dmThisModule.qryGroc do
begin
dmThisModule.qryGroc.Disablecontrols;
try
ABookMark := dmThisModule.qryGroc.GetBookmark;
dmThisModule.qryGroc.First;
while not dmThisModule.qryGroc.Eof do
begin

ShowMessage('qryGrocItem = ' + (dmThisModule.qryGrocItem.value));

dmThisModule.qryGroc.Next;
end;
finally
dmThisModule.qryGroc.GotoBookmark(ABookMark);
dmThisModule.qryGroc.FreeBookMark(ABookMark) ;
dmThisModule.qryGroc.enablecontrols;
end;
end;
end;

 

[Zathras]

The only thing wrong that I can see is that you are referencing

 qryGrocitem

in the ShowMessage while you are using

 qryGroc

in the loop.

 

[delphiman]

>The only thing wrong that I can see is that you are >referencing qryGrocitem in the ShowMessage while you are >using qryGroc in the loop.

In fact that is not wrong.

I am looping on qryGroc and displaying the progress (record-by-record) by showing the contents of qryGrocitem. Which is how I am able to tell that the entire qry is being scanned - coming to a stop at the end. Without coming out of the loop.

My problem.

 

[LucieLastic]

hi

You don't need the dmThisModule.qryGroc prefixes as you've go the With. The getBookmark should be outside the TRY aswell.


procedure TfrmThisForm.btn1Click(Sender: TObject);
var
ABookmark : TBookmark;
begin
with dmThisModule.qryGroc do
begin
Disablecontrols;
ABookMark := GetBookmark;
try
First;
while not Eof do
begin
ShowMessage('qryGrocItem = ' + (dmThisModule.qryGrocItem.value));

Next;
end;
finally
GotoBookmark(ABookMark);
FreeBookMark(ABookMark) ;
enablecontrols;
end;
end;
end;

hope that helps
lou

 

[towerbase]

Can you show us the SQL used in the qryGrocItem query ?

Have you used the debugger to single step through the code ?

What makes you think that the program has stopped on the last record ?

Have you got multiple records in the table with the same value of qryGrocItem ?

Andrew

 

[delphiman]

weez (Programmer)

I have used that code with a TTable and Paradox for years and it works perfectly. I can't understand why it wont work with a TQuery.


towerbase (Programmer)

>Can you show us the SQL used in the qryGrocItem query ?

select *
from groc t1, selstore t2
where (store_no = t2.store_no) and (area_no = t2.area_no)
order by item

>Have you used the debugger to single step through the code ?

It doesn't show what's happening. That's why I use the ShowMessage.

>What makes you think that the program has stopped on the >last record ?

Because I know what's in the Table (only 5 records in it) and ShowMessage shows me each in turn - and then stops (repeats) on the last one. If I take Show Message out I end up in an endless loop. Which I have to stop with the TaskMaster. (W2K)

>Have you got multiple records in the table with the same >value of qryGrocItem ?

It will happen. But isn't the case now.

 

[Zathras]

...coming to a stop at the end. Without coming out of the loop....

Which is it? does the program stop or does it continue to loop? I don't see how it can do both at the same time.

...where (store_no = t2.store_no) and (area_no = t2.area_no)...

should probably be:
where (t1.store_no = t2.store_no) and (t1.area_no = t2.area_no)

I'm surprised it can work at all without having store_no and area_no qualified wherever referenced.

 

[towerbase]

I don't understand how a data value is placed into qryGrocItem by the Query.

(Perhaps I've been coding queries properly in the past)

Where is qryGrocItem defined in your program ?

Andrew

 

[delphiman]

>Which is it? does the program stop or does it continue to >loop?

Program continues to loop. Routine stops progression through the table - having reached EOF - but then loops. EOF being of no effect. ShowMessage continuing to show the content of qryGrocItem in the last record.

>should probably be:
where (t1.store_no = t2.store_no) and (t1.area_no = t2.area_no)

>I'm surprised it can work at all

So am I! Yet it does otherwise. Of course I have now fixed that (Thanks!) but it has not solved the problem.

 

[Zathras]

As Spock would say, Fascinating...
What happens if you code it this way?
[blue]

  while not dmThisModule.qryGroc.Eof do
    begin
      ShowMessage('qryGrocItem = ' + (dmThisModule.qryGrocItem.value));
      dmThisModule.qryGroc.Next;
    end;

[/color]
Delphi sometimes does funny things with the with..do construct.

 

[delphiman]

Is this infuriating? Or is it infuriating? It is wasting so much time!!

If I place a break-point at B below I find that Delphi simply oscillates between Á and B.

Meanwhile from the ShowMessage I have established that Delphi is in fact scanning all the records in the Query. Because I know what each (of 5) records contains.

But for some reason EOF (or Eof) in line A is being ignored. Where I came it. :-(

with dmThisModule.qryGroc do
begin
dmThisModule.qryGroc.Disablecontrols;
try
GrocBookMark := ThisModule.qryGroc.GetBookmark
dmThisModule.qryGroc.First;
while not Eof do .... A
begin
// ShowMessage (Wha wha wha);
dmThisModule.qryGroc.Next; ...B
end;

?? Anyone ??

 

[delphiman]

I forgot to mention that I now also have the following preceding the above code. But it makes no difference.


with dmThisModule.qryGroc do
begin
SQL.Clear;
SQL.Add ('SELECT *');
SQL.Add ('FROM GROC');
Active := True;
end;
with dmThisModule.qryGroc do
begin
dmThisModule.qryGroc.Disablecontrols;

 

[Kocky]

I don't see you opening the query or calling execute. Also make sure the property QueryAllRecords is set to true.

 

[towerbase]

I think it would help if you could cut and paste the entire function from your source code without doing any editing. There is a nagging doubt that you are omitting some vital bits of evidence!

Also it would help if you could use the [ code ] and [ /code ] formatting tools.

Andrew

 

[delphiman]

FIXED!!

I really appreciate the interest and input from everyone - and this great website. And so having found the problem I feel it only fair to share it with everyone.

It was actually somewhat elusive as it has nothing to do with EOF and the code which I have above. All of which work perfectly.

Even with my omitting the t as pointed out by zathras. An eye-opener being that it actually works like that!!

My problem was the result of some obscure garbage in UponScroll of qryGROC which (for reasons which escape me - having put it there ages ago) I was doing an Edit followed by a Post.

I discovered it upon completely replacing qryGROC - and ran the routine without any EventHandlers. And it worked perfectly. I then replaced them one by one and the moment I replaced UponScroll bingo!!.

At which point I also realised that I didn't need it.

Thanks again everyone!

 

[richardchaven]

Suggestion: don't use design-time components if they have no design-time use.

For instance:

  with TQuery.Create(nil) do
  try
     DatabaseName := 'Fred';
     SQL := 'SELECT * FROM PLANTS';
     while not EOF do
     begin
      /// do something
         Next;
     end;
  finally
     Free;
  end;

This prevents any wierd design-time stuff from affecting the process.

Cheers