At detaillevel groupfooter variables are changed on page x, but not on page x+1

rbuser

Hi,

I noticed some strange behavior. If I update group footer variables at a
detail level (for instance in the Procedure DetailBeforePrint) to make a
(sub)totalization, I get the wrong values when there's a end-of-page. It
looks like on page X the procedure DetailBeforePrint executes because the
values on GroupFooter1 are changed, but on Page X+1 the values on
GroupFooter2 have not changed, like DetailBeforePrint never executed. First
or secondpass don't make a difference. I have added a MS-Word document to
make things visible.

I have tested whether using global variables show the same behavior. No, but
then skipping pages in the preview doesn't work that well.

Best regards,

Geert-Jan Fluitman
Meurs Software Nederland
(the netherlands)

nicocizik

Hi,

----------------------------------------------------------------------
TECH TIP: Performing Calculations
----------------------------------------------------------------------

Calculations can be done either on the data access side
or within ReportBuilder.

When designing reports there are always decisions to be made as to
how much processing to do on the data side versus the report side.
Usually doing more on one side can greatly simplify the other. So it is
often a personal choice based on the power and flexibility of the data
and report tools being used.


DataAccess
----------

a. Use SQL - using SQL you can perform many common calculations:

example: Select FirstName + ' ' + LastName As FullName,
Quantity * Price AS Cost,


b. Delphi TDataSets enable you to create a calculated TField object
and use the DataSet.OnCalcFields event

c. Perform any amount of data processing, summarizing, massaging
etc. to build a result set (query or temp table) to feed to the report.


ReportBuilder
-------------

Calculations in ReportBuilder are performed primarily using
the TppVariable component.

a. Set the Variable.DataType

b. Code the calculations using the Variable.OnCalc event.

c. Use the Timing dialog to control the timing of the OnCalc event.
To access the Timing dialog, right click over the Variable
component and select the Timing... option from the speed menu.

d. Set the LookAhead property to True, when you need to display
summary calculations in the title, header, group header, etc.

e. To perform calculations based on the results of other
calculations use the Calc Order dialog of the band. To access
the Calc Order dialog, right click over the Band component
and select the Calc Order... option from the speed menu.


By using TppVariable components ReportBuilder will take care of caching
intermediate results of accumlated calcs that cross pages.

There are a number of calculation examples in the main demos.dpr
project.

---

Additional Notes:

1. Do NOT use Band.BeforePrint or Band.AfterPrint. These events fire
multiple times and therefore should not be used for calculations.

2. Do NOT store results in variables that exist outside of the reports.
For example - form level variables.


--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com

rbuser

But can you also explain why a calculation done on pages X has been undone
at page X+1.

I've spend some thought on this subject and this is my hypothesis. It look
likes reportbuilder first calculates starting values for all
footer-variables per page and when this page needs to be shown it
recalculates the page. So when the starting values are not calculated
properly, calculations (in my case summerizations) are not done on page X+1,
but are on page X. This way I get totally wrong totalizations, or at least
unreliable ! Global variables don't have this problem, but give different
problems in the preview when skipping pages.

Am I right ?
How can I work around this problem ?

nicocizik

Hi,

You need to be sure you are making all calculations inside the OnCalc event
of a TppVariable in order to ensure that the calculation is made properly.
I am unsure what you mean by "global variables". Is this in RAP?

--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com

rbuser

I am enclosing a word document to show you what i mean by global values.
Maybe a bad translation. I've tried the OnCalc event and i'm afraid that
doesn't work either.

nicocizik

Hi,

For future reference, please send all attachments to
support@digital-metaphors.com.

I would first recommend getting your application working in Delphi before
moving to RAP. This gives you a chance to debug your event code to find out
exactly how the RB events behave. If you are using TppVariable objects and
their OnCalc events, the calculations made inside this event will only be
executed once. If you are executing any event code that alters the report
elsewhere, the event could fire more than once and give you wrong results.
If you are able to recreate this issue with a minimal example I could run on
my machine, please send it in .zip format to support@digital-metaphors.com
and I'll take a look at it for you.

--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com

rbuser

It is going to be verry difficult for you to find out the problem without
the testdata I'm using. Do you have an Oracle database (version 8.1.7 or
higher), so I could send you the testdata also ?

nicocizik

Hi,

Unfortunately I do not currently have Oracle installed on my machine. Is is
possible to recreate a similar situation using the DBDEMOS database included
with Delphi? Have you tried moving all your calculation code to Delphi so
you can trace it and see what exactly is happening as the report generates?

--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com