ARCHIVE: TIPS & TRICKS
Working with someone else's code
John Smiley
06.20.2000
Rating: -4.29- (out of 5)
Working with someone else's code
The scenario (all too familiar):
You have a new job, and your first programming assignment is to modify
a Visual Basic program that was written by another programmer who has
left the company. The program is hard to follow. It has no comments,
all of the variables are haphazardly named, and all the forms and
controls were left with their default names, such as Form1, Form2,
Command1, Option1, etc. You're overwhelmed.
This is not an unusual feeling. In fact, you can feel the same way
about your own code a year or so after writing it. So I emphasize these
precautionary measures to ensure easy comprehension by others:
1. Option Explicit is coded in all of your modules (this ensures that
Visual Basic enforces that all variables are declared before using
them)
2. All variables and controls are named using a formal naming
convention (i.e. Hungarian Notation)---this makes modifying the program
somewhere down the road much easier
3. Code that is repetitive in nature is consolidated into procedures
and called from within the program
4. Every module has comments describing its major functions and
features
5. Code that is anything out of the ordinary is also commented
Sounds great, but how do these 'rules' help you modify someone else's
code? Unfortunately, I'm suggesting you correct the mistakes of the
past.
Of course, before you do this, you need to get your supervisor or
project leader to 'buy into' that plan. Obviously, if he or she is
expecting the program modification to be made in about an hour, so
taking a week to clean the code and make the modification won't make
you a hit in the Employee cafeteria.
However, I can almost assure you this won't be the last time this
program is modified. Biting the bullet now and cleaning it up will
make things much easier on the next junior programmer who finds himself
in the uncomfortable position
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of modifying this code.
Once you have the go-ahead to proceed, the first thing to do is to
ensure that Option Explicit is coded in the General Declarations
Section of every module in the program. -- if it's not, add it manually
-- and then run the program. Guess what? The program no longer runs.
Why?
Coding Option Explicit will cause VB to mark, as a syntax error, every
instance of a variable that hasn't been declared---potentially lethal
errors in a program. At this point, you need to identify the variables
that haven't been declared, and explicitly declare them, with a defined
type (i.e. Integer, String, Date). While you're at it, this wouldn't be
a bad time to rename variables using either Hungarian Naming
Convention, or a naming convention in use at your company. Using Visual
Basic's Search and Replace features can make this task a lot easier
than it sounds.
With all of the variables properly declared and named properly, now is
a good time to name those forms and controls in a meaningful way. Keep
in mind that when you change the name of a control, the code associated
with it can appear to be 'lost,' finding its way into the General
Declarations Section. To avoid this, first rename any event procedures
associated with the control manually with the new name of the control-
then bring up the Properties Window for the control and change its Name
property there.
At this point, make sure the program runs okay. You'll find you now
have an understanding of how the program works -- so much so, that you
should be able to identify code that can be centralized in a
subprocedure or function. Along the way, insert comments in your code
explaining what's going on. Write those custom procedures and place
them in either a Form Module or a Standard Module (every Visual Basic
program I write has one).
Now, with the Visual Basic program nicely sanitized, it's time to code
that simple modification you've been asked to make. Hopefully it will
be a piece of cake.
Written by John Smiley, MCP, MCSD and MCT, is an adjunct professor of
Computer Science at Penn State University in Abington, Philadelphia
University, and Holy Family College, and has been teaching computer
programming for nearly 20 years. He also teaches a number of very
popular online courses at SmartPlanet and ElementK. In addition, John
is the author of four very popular Visual Basic books, and is
reportedly the first guest to write a computer program live on ZDTV's
Screen Saver's show.
John Smiley is president of Smiley and Associates,
http://www.johnsmiley.com/smass/smass.htm a computer consulting firm
located in New Jersey.
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Reader Scott Gardner asked us to remind fellow users that since the VB5 exam shall be retired prior to the VB6 exams, those opting for the VB5 exam will be required to retest sooner to keep their MCSD alive. --Editor
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