The LA Fox Developer

A Newsletter for FoxPro Application Developers in Southern California

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December 1998

Using (or not) the Value

Assign Method

by Russell Campbell

Access and assign methods have been added to VFP 6. These

are methods that are fired when a property is assigned a value

or a property’s value is accessed. For instance, you could have

a caption assign method and a caption access method. These

are not automatically part of an object, but can be added very

easily in the class designer. The methods are named with the

property name plus “_access” or”_assign”. Therefore the

caption access method is named “caption_access” and the

caption assign method is named "caption assign".

Caption_assign fires anytime you change the object’s caption

(oMyObject. Caption = “Customer”) and caption_access fires

anytime you access the object’s caption (MyVar =

oMyObject.Caption). Each property can have an access and/or

assign method associated with it.

When I first learned about access and assign methods no ideas

for immediate uses jumped out at the however my gut instinct

told me that they would come in useful. It wasn’t long before my

gut instinct proved to be correct.

I was working on a form dealing with product costs. To calculate

the total cost of a product, I had to add up the material costs,

the internal labor costs, and any outside costs. There is a

textbox on each screen that displays each of these three costs

and there is a textbox for the total cost. Each of these costs

need to be updated when other fields change. A standard

approach to this would be to have each of those fields call a

method that calculates the new cost, changes the field that

displays the new cost, and then calls a method to calculate the

total cost. Instead of using this technique, I decided that this

might be a good place to use an assign method. The fields that

related to the subcosts (quantity, price, etc.) would simply

recalculate the subcost and assign it to the related subcost

textbox. That textbox would have a value_assign method that

would in turn call the routine that calculated the total cost.

Although not an incredible simplification, it did centralize the

call to the method that calculated the total cost and it gave me

an opportunity to work with and learn about assign methods.

(Con’t, page 4)

In this issue

12 Bugs of Christmas

John Rivard Interview

Dates and Time

At LA Fox

December 21, 1998, 6:30 PM, Ken Levy and The Annual LA

Fox Christmas Party. It’s that time of the year again. Come

join us for merriment, good times, fox fellowship, and tasty

treats. Ken will be demonstrating the latest and greatest of

whatever he’s been working on and The White Elephant Gift

Exchange will be happening again. So come prepared for a

good time. For more on the Christmas Party, see the article on

Page 13.

January 18, 1999, 6:30 PM, Miriam Liskin. Miriam is ex-

tremely well-known for her contributions to the FoxPro commu-

nity. She writes a regular column for FoxPro Advisor and has

authored many books on the subject of FoxPro application

development. Her most recent books are Miriam Liskin’s Visual

FoxPro Expert Solutions (Que) and PC Magazine Programming

FoxPro 2.5 (Ziff-Davis). Miriam’s presentation on Builders was

one of the highlights of the August conference. This night, to

paraphrase Monty Python, she’ll be presenting something

completely different. You don’t want to miss this one.

Elsewhere

VISUAL FOXPRO DEVCON 99, June 6-10 Palm Springs.

The Tenth Anniversary of Microsoft Visual FoxPro and DevCon!

Don’t miss Tenth Anniversary VISUAL FOXPRO DEVELOPER

CONFERENCE 1999, the annual gathering of FoxPro develop-

ers from around the world. VISUAL FOXPRO DEVCON is

essential technical education for serious FoxPro developers.

(Con’t, page 2)

Page 3

Page 5

Page 8

and much more!

Out and About

by Barry R. Lee

The December meeting of LA Fox will be

held on Dec. 21, 1998, at 6:30 PM at our

regular meeting place (the Torrance Airport,

3301 Airport Drive, in Torrance). For details

on how to get there, see the map on the back

page.