Broken VI When Creating a Concrete Implementation of an Abstract Message with Variant Input

[Dan_K]

I think I found an error in Actor Framework. I created an abstract message that uses a single variant as it's data type. When creating a concrete implementation of this message the Do.vi is broken.

I used Create Child of Abstract Message from the right-click menu in the project.

The final VI looks like this (It's also in the Step 2 project):

It's an easy fix, and this doesn't occur when creating a normal message, only when creating a child of an abstract message

[Oli_Wachno]

Hi Dan,

I remember dimly having seen a behavior like this back in LabVIEW2013. I think I have worked around this NOT using variant data....

But it' been  a while...

If I may ask: what is your use case for having a variant message parameter?

BR

Oli

[Dan_K]

I am using a nested actor off of the root to provide a data distribution service based on pub/sub throughout my application. Each topic can be a different data type and I didn't want to create a bunch of abstract messages. I just convert to and from the topic data type in the concrete implementations.

[Oli_Wachno]

Dan,

I'd recommend a different approach:

Define an abstract message class (dierctly inheriting from AF message). No properties, only one method: override of "Send Message" for this class and it's successors.

Based on this abstract class, define a decent hierarchy for (less abstract) messages and their successors.

The trick is is to contain the data needed in the properties of the concrete message classes.

This might seem a bit more complicated at first, but I think it's a much cleaner approach, that saves you manual casting of variant data to concrete data type (which can cause a lot of trouble without proper error handling)

A good presentation to look at is also Casey Lamers' presentation at NIWeek 2018