"Previous" value won't Post to field

[Sid Frasier]

I needed to use the a field value from the Previous record to calculate current balance. I setup a field to capture this value called TEMP. In the field rules, I used calculate feature to define the expression...
Previous(current_value). The cuurent_value field expression was TEMP+ADJUSTMENT (which added adjustment to previous "current_value").

In the entry table the values appeared as expected until I saved the record... the TEMP field went blank, and the result was simply the ADJUSTMENT value. Is this a bug or am I missing something? The previous value was called and appeared properly but vanished as soon as the entry record saved. (A5V5)

[forskare]

RE:

...I setup a field to capture this value called TEMP...

Maybe it takes the name of the field for a literal intrepretation? Seriously, Why did you name the field Temp? Because it was intended to only temporarily store a value? I'm suspecting you've got something in you setup to do just that. If so, you'll need to make a change.

kenn

[Sid Frasier]

RE:

Actually I tried to use the "Previous value command" into the direct expression and got the same result.
The current_value field expression was: previous(current_value)+ ADJUSTMENT (which added adjustment to previous "current_value").
Here again the new value was correct until the record was saved. At that point it appears previous(current_value) vanishes... really weird. Why would the statement be invalid after it attemps to save the record?

[Tom Cone Jr]

RE:

Sid,

May I ask why you're storing the adjusted balance in the current transaction record? Many designers wouldn't do it, since the figure will be wrong as soon as the user adjusts any of the earlier transaction records later on. It's also easy to compute the current adjusted balance just from the transactions table, whenever needed for a form or report, so why go to the trouble of computing it each time a transaction record is saved? If I've misunderstood what you're describing, I apologize, but thought I'd ask...

-- tom

[rtbtat]

Running Balance?

I thought Tom made an excellent point, so if you stay with the running balance methodology, I think you should follow his advice.

Although many developers use the running balance method, I personally have a couple of issues with that methodology. In addition, I much prefer using what I think is a more intuitive and easier paradigm. Why don�t you think about using two child tables, one for debits and one for credits, both linked to the parent table by a field such as Inv_No or Acct_No?

Next, do the following in the parent table. Create one field to store the total debits for that invoice or account , and one field that stores the total credits for that invoice or account. You will also need a third field called BALANCE, which is a simple calculated field [Debits � Credits]. In essence, this third field will replace what you are currently calling your running balance.

Every time a debit or a credit is entered into one of the child tables, you have at least two choices

[1] You can post the amount of the debit or credit to the appropriate field in the parent table

or

[2] You can do what I do and love, thanks to a fantastic tip from Steve Workings. You can write a relatively simple Xbasic script that calculates the total debits or credits for that invoice or account, each time a child table transaction is entered. This script then replaces the old value of the debits or credits in the parent table with the new total.

Using such a methodology is very simple and the users will automatically see the new and updated CURRENT BALANCE in the parent table portion of your data entry form every time a debit or credit is entered into a child table.

Robert

[Sid Frasier]

RE:

Tom-
Users dont have direct access to this table.
it provides cashdrawer balances based on the cash added or removed in a transaction in the field called "Adjustment" which is then added to the last record "current_value." The cash in the drawer is previous(current_value)+ ADJUSTMENT.... seemed like the most straight forward way to go!!

[Sid Frasier]

RE:

As you can see I've been messing with this previous value/record command for a couple of weeks.

The latest version of Alpha 5 V5 made it work to some degree, but unless you're using it directly in the Table the field expression applies to it it doesn't work properly. If I use a form or a set it won't post the value properly... then I have to run an update operation to apply the value. The functional description of the previous("field") is non-existent as near as I can tell.

The application is so basic, I can't understand why there isn't a simple answer. All I want to do is take a positive value and a negative value create an algebric sum and add that to the sum found in the previous record... not a rocket scientist chore even though it has turned out to be in Alpha 5.

Here is the simple field expression: previous("balance")+ (positive_value - negative_value)
This should take the value in the "balance" field last record and add it to the sum of the positive and negative fields. As I said it works fine as long as you work inside the TABLE where the field is specified.

Any rocket scientists out there????

[Sid Frasier]

RE: Running Balance?

Robert,

I've tried posting the debits and credits to a parent table but it is necessary to get the previous balance from somewhere. The posting process requires me to run an update operation to make the expression actually calculate in the field.
I want the transaction to be recorded so the user can verify debits and credits, based on other entries.

2 other people have emailed me asking if I found a solution, but so far I can't figure it out.

[russ Boehle]

RE:

What Tom and Robert say is good advice but if you want to keep the running balance this way you might try putting xbasic on the onsave event for the form that
puts the value of the balance field in a variable and then adds it to the value in the other field. (not sure I have the field names straight). This can be done with action scripting pretty easily.

If what you want is a running balance, I have found this to be harder than I thought using events (for me anyway) but can be done using a simple table to hold the balance amount and using posting.

Russ