Initialising variables!

[mctozzy]

I seem to be having a problem with initial values for Variables. What I want to do is create a running balance value, so I have a variable with Calc type Sum, Reset type = Report, Increment=none.

 

I have a variable expression such as $F{Amount}.

 

This works correctly, except for one thing. I want to prime the value of the variable, so that it starts off with an "Opening Balance" so to speak.

 

The initialValueExpression doesn't seem to work in the way I would have expected. No matter what I do, the initial value is always zero.

 

Thanks,

Milt.

[teodord]

Hi,

 

This is because the initValueExpression is used only for obtaining a value to display before the variable is actually incremented the first time.

If we are talking about a SUM and we want it to start with 5, not 0, then you should add the 5 in the expression of the field that displays the sum, or have a separate variable with calculation Nothing that adds the 5 to the sum variable.

 

This is because the initValueExpression of a variable is not considered as part of the series used to increment the variable during iteration. This initial value is only for displaying purposes, before the variable incrementing kicks off.

 

I hope this helps.

Teodor

[mctozzy]

Thanks for the explanation. By creating a second system variable, I assume you meant this:

 

(using "pseudodefs")

 

$V{RunningBal} := sum($F{Amount})

 

and

 

$V{Balance} := system($V{RunningBal}+$P{InitialVal})

 

Then using $V{Balance} in the report?

 

I can see that would work, but I don't really understand why there isn't a more natural way to prime a variable, without having to resort to this or use scriptlets.

 

Why not extend the meaning of InitialValueExpression to actually prime the variable?

 

Is this worthy of an RFE?

 

Cheers,

Milt

[lucianc]

Not sure what you mean by "system" variable. You simply need to create a new variable with calculation="Nothing" and $V{RunningBal}+$P{InitialVal} as expression. And in any case you don't need scriptlets to do this.

 

Regarding the "extension" of the logic of initialValueExpression, two notes:

Changing this does not strictly involve "extending" the semantics of initialValueExpression, it actually breaks backwards compatibility. People will witness altered behaviour in certain scenarios. It's never trivial to take a decision in such a case.

Base/starting value makes sense for calculations such as Sum or Count, but it doesn't for others like Average or StandardDeviation. Such a functionanily would be then slightly inconsistent across calculation types.

[/ol]

 

Regards,

Lucian