By Mahbod Morshedi
I m trying to build a software, and data management has become too complex. In short, it is acquiring data from three channels and doing some calculations and then showing and reporting that data for the user to make a fitting decision. The user then, can save the file and import the saved worked-up file later to view or manipulate.
The data consist of three interdependent data set, and so far, I have collected the dat as an array of clusters (size 3) for three sets and kept user input data in the same manner. I am also using a simple "producer/consumer" design. However, I think that may have been a mistake, and I might be able to do a better job using either actor or QMH design, especially since I need to think about adding the acquisition part (which is not yet developed). The thing is that I have not used oop before at all and am not quite sure if this is the correct approach and how should I bundle my data. Considering that the data (not all but some) need to be accessed by other classes if I goo with oop.
For example, should I keep the data as separate class data and use methods for override or keep it as an array in the parent class and use static methods and only use child classes for graphing. These are the type of questions I am struggling with. Also, can anyone help me decide between DQMH, Actor or just standard Producer/Consumer patterns, please? I am completely lost.
Thank you in advence.
This is how the front pannel looks like:
And this is the data set for the system (which I am keeping as an array) there will me more data added to this as the capabiliy grows.
I tried to create a template based on OOP for QMH. During development I have been confronted with infinite crashes of LabVIEW so I decided to slow down with this project and open it to the community. I finished my working example and stopped for now.
So if anyone is interested to play around with the code, see attached ZIP file (LV 2020).
By Marko Hakkarainen
I had some time to learn about new interfaces and finally I could implement my collection class as I had envisioned. I didn’t want to use iterable and iterator names, because I thought that would have been too bold a claim.
The original version of the collection class was (and is) used as a collection of sequence steps. Each element can be either a sequence command (send message, wait timer, wait complete etc.) or another collection of commands (sub-sequence). That’s the reasons for the labels and search method. Otherwise it is just a fancy (Rube Goldberg) array.
Next method is recursive and it steps through all elements in the collection. Execute is only method, which requires override.
For now, it’s at least an exercise in new interfaces. I don’t know if it’s useful enough to be in the code repository, but I can polish it up if needed.
Certified LabVIEW Architect
Iterable Collection LV2020.zip
By Jim Kring
[Update: NI Bug 974336]
There seems to be a bug in the coercion of data to variant when a cluster contains a single element that is a variant. (original post here).
Note: This bug appears to be very old, going as far back as LV2012. This has been reported to NI in the LV2020 Beta forum. I don't have a Bug ID / CAR yet.
Coerce to Variant Fail (LV2019).vi
Note that adding another element to the outer cluster causes the problem to go away.
I'm running into something I don't really understand. Maybe you can help me here !
I've got a LVLIB that is used as an 'Interface': it exposes public VIs which wrap around public functions of a private class (see code attached) . The class is private because I want to force the users to use the 'interface' functions.
In one of my interface VI, I create a DVR on the private class (Interface_init). The DVR is stored into a typedef (FClass_DVR.ctl) and this typedef is the 'reference' that link all the interface public functions.
In TestCode.vi (which is not part of the lvlib and illustrates the standard code that a user can create to use my driver), I can call my public interface functions and link them without any problem.
But as soon as I create an indicator on that reference (to create a state-machine-context-cluster for example), my TestCode VI breaks !
The error returned is : This VI cannot use the LabVIEW class control because of library access scope. The LabVIEW class is a private library item and can only be accessed from inside the same library or libraries contained in that library.
I understand that the class is private. But the DVR is contained into a public control. Using an In Place structure on that DVR into TestCode would not work, since the class is private. So why is the DVR control problematic at that point ? Creating it do not breaks any access protection...
Am I missing something ?
DVR Private POC.zip