Possible bug with ReportBuilder 10.02 Enterpsise with Delphi 7
In one of our reports, using ReportBuilder, there is some calculations
made inside the event BeforeGenerate of a Detail band.
The result of this calculation is showed on screen correctly. But, when we
print this report, the value appears doubled on paper.
Debugging the application we found that the event BeforeGenerate is called
*at least* one time before the report is shown on screen and right before
the report is about to be printed. Thus, giving us the doubled (and
incorrect) result.
Is this the normal behavior of the component? Should this particular event
be called "twice"?
If this is the case, we will have to redo most of our reports because we
have many calculations in these events.
Thanks in advance.
--- posted by geoForum on http://delphi.newswhat.com
made inside the event BeforeGenerate of a Detail band.
The result of this calculation is showed on screen correctly. But, when we
print this report, the value appears doubled on paper.
Debugging the application we found that the event BeforeGenerate is called
*at least* one time before the report is shown on screen and right before
the report is about to be printed. Thus, giving us the doubled (and
incorrect) result.
Is this the normal behavior of the component? Should this particular event
be called "twice"?
If this is the case, we will have to redo most of our reports because we
have many calculations in these events.
Thanks in advance.
--- posted by geoForum on http://delphi.newswhat.com
This discussion has been closed.
Comments
Thanks for your answer Paul, but I'm afraid I don't quite follow you.
I couldn't find any mention to those timing events that you talked about
in the component TppReport, nor in other components of the RBuilder tab
that I looked.
Would care to elaborate more on the subject please?
Nonetheless I saw another event that maybe could hold some calculations
reliably, the OnStartFirstPass event. Then I did a search here in the
Mailing List and found that someone also have had trouble regarding the
event "double-firing" execution.
--- posted by geoForum on http://delphi.newswhat.com
Calculations inside a report should primarilly be made in the OnCalc event
of a TppVariable. If you must make a calculation elsewhere, you will need
to take into account that the event may fire more than once. There is no
way to be sure any other events will only fire once per iteration in
ReportBuilder.
----------------------------------------------------------------------
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
Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com
Following your tips we managed to get our calcs right and to understand
the machanics of ReportBuilder.
We were definitely wrong using the band's events to do our math. We got
this bad habit from another reporting component.
Thank you again and congratulations for your solid product. We'll surely
mention it to other softhouses that we are partner of.
-Bernardo Lopes
--- posted by geoForum on http://delphi.newswhat.com