a question about the OnPrint event of a summary

rbuser

Hi,

I've programmed a simple counter which increases a global variable.
On every OnPrint event of the summary of a subreport, the variable is
increased by one.

So far so good.

But it never counts correct. After debugging I've noticed that at the
OnPrint event is fired once already, before the first summary is printed.

But the OnPrint event of the LAST summary is NOT fired (although the summay
is visible in the report).

I've tried other event (OnGenerate, BeforePrint etc etc), but that has the
same effect.

Whats wrong??

TIA

Rob

nardmoseley

You need to use TppVariable components to perform calculations. The
TppVariable has an OnCalc event that can be used to set the
TppVariable.Value.


------------------------------------------------------------------------
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.



--
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--
Nard Moseley
Digital Metaphors
http://www.digital-metaphors.com