| How to re-use object methods [message #85788] |
Sun, 08 September 2013 10:30  |
wlandsman
Messages: 743
Registered: June 2000
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Senior Member |
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I learned object programming late in my career and have come to appreciate its many benefits. But one thing I have not figured out is how to make the code re-usable.
I have access to a very large object widget display program. Much of the widget is for a rather specific application, but some of the buttons, say, "Contrast" could be used in other widget display programs. So when writing my own widget program, I add a "inherit largeobject" to the object definition so that it can inherit the methods of the large object widget. But I immediately got conflicts between my object definition parameters and those in the large widget display. I have to admit I did not try very hard to debug this, in part because I was hesitant for my 500 line program to be inheriting the 50,000 line largewidge object. I ended up forgetting about inheritance and just cut and pasted the the portions of the largeobject methods I needed to create methods for my own object.
I wonder if the way to make the make the code more re-useable would have been for the author of the large widget program to have made each button in the large widget program into an object, rather than a method.
Thanks, --Wayne
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| Re: How to re-use object methods [message #85791 is a reply to message #85788] |
Mon, 09 September 2013 05:44  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Wayne Landsman writes:
>
> I learned object programming late in my career and have come to appreciate its many benefits. But one thing I have not figured out is how to make the code re-usable.
>
> I have access to a very large object widget display program. Much of the widget is for a rather specific application, but some of the buttons, say, "Contrast" could be used in other widget display programs. So when writing my own widget program, I add a "inherit largeobject" to the object definition so that it can inherit the methods of the large object widget. But I immediately got conflicts between my object definition parameters and those in the large
widget display. I have to admit I did not try very hard to debug this, in part because I was hesitant for my 500 line program to be inheriting the 50,000 line largewidge object. I ended up forgetting about inheritance and just cut and pasted the the portions of the largeobject methods I needed to create methods for my own object.
>
> I wonder if the way to make the make the code more re-useable would have been for the author of the large widget program to have made each button in the large widget program into an object, rather than a method.
The fact that IDL's objects are implemented as named structures really
gets in the way of object inheritance. Foresight and a great deal of
care is needed to be sure there are no overlapping field names is the
final, combined structure. Since this is nearly impossible to do in
practice, it limits IDL objects to "shallow" inheritance trees.
In your case, I think you were wise to pick the parts you needed for
your new object and just paste them in, with field name changes, if
needed, for the new object.
Once you become more familiar with objects, you will probably switch
from writing one "very large object widget" program, to writing many
much, much smaller ones that can be combined (but not necessarily
inherited) into other large widget programs. That's when objects will
start to make sense to you as "reusable" parts of your library.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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