Creating Plugin Modules for Use with Compiled Code

Question

Hi all,
While programing a data analysis package in Labview, I've run into a problem that I don't really know how to answer.  It goes something like this: my program receives data from measurement devices in the form of ASCII or binary files, which I must then process and evaluate.  The problem is, the data files can have a variety of different formats.  Right now, I only know of 4 or 5, but more could literally be added at any time.
My thought is this: I'd love to have some sort of modular plugins for reading the data files.  In other words, I could have a subfolder under my application's space in the "Program Files" directory.  The subfolder would contain any number of "ReadFileX.xxx" modules.  Upon initiation, my code would scan that folder, determine the possible formats (based on the *.xxx files therein), and be capable of reading any of the files.  Ideally, the user would select a file, I would note its format, and call the appropriate plugin module to handle reading the data into my code.
What is the best approach for doing something like this?  I looked (briefly) into using DLL's, but (from what I can tell) I would need to explicitly define the function name and the inputs / outputs in the "Call Library Node" function.  This would appear the break the modularity feature, as I want to be able to load the software, and then develop new plugins down the road when the need arises.  I also found some information on source distributions (in an LLB).  This option would probably work, but my efforts at coding a basic test of VI-Server were met with errors.
Does anyone have any experience performing a similar task?  If so, would you share your knowledge / secrets with me?  I would be extremely grateful for your feedback.
Thanks!
Mark

Answer 1

Mark - there is a Coding Challenge currently going on, and I have submitted an entry that shows how to dynamically instantiate a class based on a class that resides on disk. Specifically, you're going to be interested in "Get LV Class Default Value.vi" under the "Cluster, Class, and Variant" palette that allows you to create an instance of an object based on the path of the .lvclass file. The class you load is going to be what's called a child class of a parent class (or base class), where the child class implementation overrides the function of the parent class. The "Get LV Class Default Value.vi" is very loosely analogous a Class Constructor.
You can deploy your application having implemented all the base class functions, then subsequently develop and deploy new classes to reside in a "plugins" folder without needing to change the original app code.
If you find that contest entry helpful, consider dropping a vote, huh? The LabVIEW Communities have had access errors sporadically the past few weeks, so if you get a "Server Error" you may need to try again later. There's also going to be Forums maintenance today and tomorrow.
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