how to use an array

[John Keogh]

I've been searching through the forums and the local help file for this but don't quite understand what to do.

I want to build a lookup filter using an array (someone told me this was the way to go).

Where is the best place to start to try to understand what I'm doing?

John

[G Gabriel]

Re: how to use an array

Start with the help file.

[John Keogh]

Re: how to use an array

Thanks for the reply

I've been there.

My problem is I'm working on a project that is beyond my present ability. Hence my question.

[Tom Cone Jr]

Re: how to use an array

John, tell us what you're trying to accomplish. A "lookup filter" is simply an expression that describes the records to be retrieved from a table. Not clear why you'd want to put that in an array.

Perhaps you're talking about running a query against a table, and then reading through the filtered records one at a time in order to store field values from each record in an array?

[John Keogh]

Re: how to use an array

I have a clothing rental business. I allocate "hired" items to my customers between two dates, collect and return. This works perfectly for me with one machine doing the reservations.

Business is good I want to move to more than one machine, my problems begin.

Presently I query my stock and set a logical field to true if an item is booked. However if a second PC does the same for different dates my booked logical field gets over written with the latest query results.

OK for machine 2 not OK for machine 1.

Apparently an array is the answer as this will get round this problem.

I have tried reading the help file and looking at hotel reservation solutions on the message board but I'm a bit out of my depth

John

[Tom Cone Jr]

Re: how to use an array

John, I think reservation systems are among the most complex to design. It's not clear to me why an array will help you here, but I leave that to others. There are probably more elegant approaches but to me the simplest course would be to rethink your data structures.

If you rent clothing by the day I'd have a table that contained a separate record for each day an article of clothing was booked. If the garment were booked for 4 days in a row I'd have 4 records, one for each day. A simple search of this table based on garment id and a single date would show you if it's available or not. In other words I'd try to stop thinking of the garments as the items you're billing. It's really the days of use, or simply, the days, that you're billing. Each day is like a line item on an order or invoice, if you see what I mean.

That's about the extent of what I can contribute here, but I'll be watching cause it's a matter of interest. Hopefully others with more experience on this type of app will chime in to confirm or correct my suggestions, and offer more guidance.

[G Gabriel]

Re: how to use an array

Apparently an array is the answer as this will get round this problem.

Not the only answer and won't resolve overbooking issue which is a query flaw.

Leave arrays aside for now. What you need to do first is to address this issue:

However if a second PC does the same for different dates my booked logical field gets over written with the latest query results.

The second machine should first query those records where the booked field is false. Then you will have a myriad of ways to show what's available, array is simply one way but not the only one.

[John Keogh]

Re: how to use an array

Thanks for this input

I think I understand what you are saying. So machine 2 is now looking at all unbooked stock but does this not mean that machine 2 is excluding stock that may be available to its set of dates.

Also would machine one start to see machine 2 booked stock as unavailable?

Would this be copied to a local file on each machine on the network?

John

[G Gabriel]

Re: how to use an array

If you are on a network, both machines will be working on the same table. It is no different than working with one machine with the exception that with a network you could:
a. Access the same table by more than one machine AT THE SAME TIME and/or
b.Access the same table from More than one location.

But the structure of the query is the same regardless of how many machines access the table.

You have to put in place a scheme that tells you what's available when.

[John Keogh]

Re: how to use an array

(Date_of_return >= Var->vdCOLLECT ) .and. (Date_of_collection <= Var->vdRETURN )

This is the expression I presently use to mark all the booked items as true then my lookup filter is as follows. The important bit is Booked=.f. the rest is for ease of use for the operator

Booked=.f..AND.containsi(Kilt_Description, personal_details->tartan).AND.containsi(Kilt_Size, personal_details->kilt_size).

Can you suggest what I need to do to resolve my second machine problem

John

[MoGrace]

Re: how to use an array

Hi John,
I think Tom has the right idea on needing more tables to find when an item is booked. Certainly people try to schedule in advance don't they? If the Item is marked as booked and the dates are part of that table then how can future dates be scheduled? If instead you pull up an item and enter bookings into a linked table then you can reverse the set to see the items booked for the date range you are looking for.

[G Gabriel]

Re: how to use an array

You needed Columbo to figure this one out!

When I first looked at your last post, everything seemed just fine and I was about to respond that you are doing what you should be doing.. then I saw that cigarette butt that seems to always tip off Columbo to the real killer.

Here is the cigarette butt:
(Date_of_return >= Var->vdCOLLECT ) .and. (Date_of_collection<= Var-> vdRETURN )

Now I could be wrong and this whole Columbo theory could be just a fantasy, but it seems to me that:
1-You are marking records as true based on two variables vdCOLLECT & vdRETURN
2-Then when you do the same from the second machine, the values of these variables are different from those in the other machine, hence you have the overlap.

Variables are not shared over a network. They are local to your machine.

[JohnZaleski]

Re: how to use an array

John,
If you use Tom's suggestion for creating a booked item by day table,You will not have to mark records when querying. There is isually an optimal design to solve a business problem. Your present design is not optimal. Your present design works for you in a single user environment, but not in a multi-user one.By creating an index tag combining the item code and the rental date, you can instantaneously see if a particular item is available on a day or for a range of days.

Sometimes it is necessary to abandon a previous design and redesign. If you do the ultimate solution will be simple.
John

[John Keogh]

Re: how to use an array

What would I do get alpha to create these entires automatically. I remember a long time ago on this message board one of the gurus telling me it was not a good idea to have alpha create its own records.

I have been thinking about redesiging but when you have used one approach for many years it s hard to make that move.

Maybe the time is right to make that change.

John

[MoGrace]

Re: how to use an array

What would I do get alpha to create these entires automatically. I remember a long time ago on this message board one of the gurus telling me it was not a good idea to have alpha create its own records.

I have been thinking about redesiging but when you have used one approach for many years it s hard to make that move.

Maybe the time is right to make that change.

John

If you have a date range then getting the number of records to add could be done with some date subraction to get a count for using in a FOR NEXT loop with table.enter_begin() - a button script could do it.