Hello all!
Has anyone heard of or have experience with problems regarding subclassing
more than a certain number of times?
Ex: VFP -> myBaseClasses -> myComponentClasses -> appClasses ->
subAppClasses
Thanks for your input!
--Brad
Author: RSA Forward, eleafe@RSA-NET.COM
Posted: 1999-09-10 09:05:38 Link
>Has anyone heard of or have experience with problems regarding
>subclassing more than a certain number of times?
No, that isn't a problem from a technical POV. At one Devcon, Calvin Hsia
demonstrated a class hierarchy of 100 levels (generated programmatically, of
course!), and that was still wicked fast. I belive the only hit comes at compile
time, not at run time.
However, any hierarchy more than a few levels deep might be problematic
from a desing POV. Make sure you aren't creating one-off classes, or subclasses
which differ only in a few property settings,
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Ed Leafe
Author: Wolfe Stephen S Civ GS-11, Stephen.Wolfe@macdill.af.mil
Posted: 1999-09-10 10:42:48 Link
What do you mean by one-off classes?
Stephen S. Wolfe, GS-11, DAF
Senior Network Engineer, Medical Information Services
DSN 968-6930 Comm: (813) 828-6930
Email: wolfess@macdill.af.mil
-----Original Message-----
From: eleafe@RSA-NET.COM [SMTP:eleafe@RSA-NET.COM]
Sent: 10 September, 1999 9:06 AM
To: Multiple recipients of ProFox
Subject: Re: Multi-Level Subclassing
>Has anyone heard of or have experience with problems regarding
>subclassing more than a certain number of times?
No, that isn't a problem from a technical POV. At one Devcon,
Calvin Hsia
demonstrated a class hierarchy of 100 levels (generated
programmatically, of
course!), and that was still wicked fast. I belive the only hit
comes at compile
time, not at run time.
However, any hierarchy more than a few levels deep might be
problematic
from a desing POV. Make sure you aren't creating one-off classes, or
subclasses
which differ only in a few property settings,
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Ed Leafe
Author: RSA Forward, eleafe@RSA-NET.COM
Posted: 1999-09-10 11:08:14 Link
>What do you mean by one-off classes?
A class is a template from which objects are created. If you have a class
which is only ever used by one other instance/subclass, chances are that a
re-design is in order. IOW, it probably looked like a class when it was created,
but subsequent development has indicated otherwise.
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Ed Leafe
Author: Gene Wirchenko, genew@shuswap.net
Posted: 1999-09-10 12:59:26 Link
>>What do you mean by one-off classes?
>
> A class is a template from which objects are created. If you have a class
>which is only ever used by one other instance/subclass, chances are that a
>re-design is in order. IOW, it probably looked like a class when it was
created,
> but subsequent development has indicated otherwise.
I do it all the time! My forms are all one-offs. I subclass them off
my main forms handling classes and add PEMs to taste.
What I don't do is subclass off of these one-offs.
Sincerely,
Gene Wirchenko
genew@shuswap.net
Computerese Irregular Verb Conjugation:
I have preferences.
You have biases.
He/She has prejudices.
Author: Paul McNett, pmcnett@pcs-blc.com
Posted: 1999-09-10 13:16:36 Link
Ed, are you implying that it's better to create SCX forms instead of
form classes? I have a couple layers of form classes, the bottom
layer being "one-off", as you describe.
On 10 Sep 99, at 11:08, eleafe@RSA-NET.COM wrote:
> >What do you mean by one-off classes?
>
> A class is a template from which objects are created. If you have a
> class
> which is only ever used by one other instance/subclass, chances are that a
> re-design is in order. IOW, it probably looked like a class when it was
> created,
> but subsequent development has indicated otherwise.
>
>
> ___/
> /
> __/
> /
> ____/
> Ed Leafe
>
>
>
>
>
Paul McNett
Computer Consultant / Custom Application Developer
Professional Computer Solutions
Hollister, CA 95023
mailto:pmcnett@pcs-blc.com
Author: RSA Forward, eleafe@RSA-NET.COM
Posted: 1999-09-10 13:57:21 Link
>Ed, are you implying that it's better to create SCX forms instead of
>form classes? I have a couple layers of form classes, the bottom
>layer being "one-off", as you describe.
No, not at all. In that case, the final item, whether a VCX or an SCX, is
essentially a concrete instance of its superclass. This is different than a
class which has only one subclass, but whose subclass is used in many ways. In
this case, the intermediate level can probably be eliminated with only minor
re-design. Or, for those who use SCX forms, if the superclass of the SCX is used
only for that SCX, then it probably can be eliminated, too, as any class-level
customizations can be simply added to the SCX.
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Ed Leafe
In a message dated 9/10/1999 8:12:51 AM Central Daylight Time,
eleafe@RSA-NET.COM writes:
<<
However, any hierarchy more than a few levels deep might be problematic
from a desing POV. Make sure you aren't creating one-off classes, or
subclasses
which differ only in a few property settings, >>
What Ed says is correct. Another problem, which I feel is even more
important, is that with more than 4 levels of subclassing, you'll really
create a maintenance nightmare. Not mention an un-debuggable debacle. :^)
Instead of going over-board on inheritance, please consider composition!
Happy Dae.
Author: Michael Babcock, mbabcock@kepro.org
Posted: 1999-10-08 11:44:12 Link
I have a subclassed form "frmDates". I want to use class, but slightly change
the functionality of two of its textboxes right-click event. Must I do
another DEFINE or is there a way to directly change the logic for an item for
this instance only? Examples are greatly appreciated!
'sortof' pseudo-code of what I want to accomplish:
oFrm = createobject("frmDates")
oFrm.MyTxtBox.rt-click procedure = <change of logic>
TIA,
--Mike
********************************
Michael Babcock
KePRO, Inc.
Tel: 717-564-8288
Fax: 717-564-4188
Internet Address: mbabcock@kepro.org
Home Page: http://www.kepro.org
********************************
Author: Ed Leafe, ed@leafe.com
Posted: 1999-10-08 11:59:29 Link
On 10/8/99 11:44 AM, Michael Babcock supposedly said:
>I have a subclassed form "frmDates". I want to use class, but slightly
>change
>the functionality of two of its textboxes right-click event. Must I do
>another DEFINE or is there a way to directly change the logic for an item for
>this instance only? Examples are greatly appreciated!
>
>'sortof' pseudo-code of what I want to accomplish:
> oFrm = createobject("frmDates")
> oFrm.MyTxtBox.rt-click procedure = <change of logic>
You cannot modify the code of an instance. You'll either have to
subclass, or bracket your RightClick() code to do different things based
on some form property:
DO CASE
CASE Thisform.cBehavior = "Foo"
{do 'foo' right-click stuff}
CASE Thisform.cBehavior = "Bar"
{do 'bar' right-click stuff}
ENDCASE
Then when you create your form, do the following:
oFrm = createobject("frmDates")
oFrm.cBehavior = "Bar"
oFrm.Show()
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Ed Leafe