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 Ram Prakash
Can anyone please tell what a DVR [ Data value reference ] is ? I want to know at what situation it will be used and what are the advantages we get by using DVR. I am really confused in this topic . If someone has any code in which they have worked with DVRs. kindly share it to me.
By Ryan Vallieu
I have seemingly found an issue with the shipping example code for Nested Malleable VIs. Another user has verified that he saw the same behavior in 2019.
I am working through the examples and the presentation from NIWeek 2019. In running the Lesson 2b code (C:\Program Files (x86)\National Instruments\LabVIEW 2019\examples\Malleable VIs\Nested Malleable VIs) I found the Equals.vi in the class was not being leveraged and the search failed. When I went to my LabVIEW 2018 machine and ran the Lesson 2b.vi the code worked to find the element by correctly leveraging the in-class Equals.vi.
One difference I see is that in the 2018 example the Equal.vi is in the example folder with the code, and in 2019 the Equal.vi has been moved to VI.lib - otherwise the code looks to be the same. The Equals.vi code looks identical, and the calling VIM look identical. I posted on the LabVIEW NI.com forum here:
I am trying to determine what may have broken or changed between the implementation in 2018 and 2019, visually the code looks the same.
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