On Aug 25, 2006, at 7:14 AM, Thorsten Hohage wrote:
Does anyone know of any code hacks that would allow a developer to
instantiate a custom class from within the IDE by name?
example:
dim instance as Object = NewInstanceOfObjectByName("MyCustomClass")
This is an example of something you could implement elegantly with
"first class classes" (classes that are themselves objects). If you
are interested in this capability, sign on to <http://
www.realsoftware.com/feedback/viewreport.php?reportid=ngrccqde>.
Until then, your simplest solution is a dirty big case statement.
Sorry, but IMHO the simplest solution is a "class-factory"
Define a dictionary e.g. in the App (or better some where else, so
your code is protable between Applications) and add the classes
during start up
Permit me to elaborate. A factory function is a good solution to
this, but it doesn't provide what the original person was looking
for, which is something more loosely coupled and easily extensible.
But first-class classes, suitably designed, do.
If classes were themselves objects, with constructors and able to
support polymorphism (a "Shared Interface", meaning the shared
methods on the class allow the class to be treated as an instance of
a type), then in the class's constructor, it can register itself with
the factory, installing itself into the dictionary you suggested, and
manufactures instances of itself on request. Now, the factory works
as in your solution, but the code is more loosely coupled: you can
add new classes, delete classes, whatever, and you never have to
change the factory.
Guyren G Howe
Relevant Logic LLC
guyren-at-relevantlogic.com ~ http://relevantlogic.com
REALbasic, PHP, Python programming
PostgreSQL, MySQL database design and consulting
Technical writing and training
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