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
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
I currently have a project that I am refactoring. There is a lot of coupling that is not sitting well with me due to typedefs belonging to a class, then getting bundled into another class which is then fired off as event data.
Effectively, I have class A with a public typedef, then class B contains ClassA.typedef and then class B gets fired off in an event to class C to be handled. Class C now has a dependency on class A which is causing a lot of coupling I don't want.
For my real world example I query a bunch of data from our MES, which results in a bunch of typedef controls on the connector panes of those VIs. Those typedefs belong to the MES class. I then want to bundle all that data into a TestConfig class and send that via an event to our Tester class. But, now our tester has a dependency on the MES.
I see a few ways to handle this. First is move the typedefs currently in the MES class, to the TestConfig class. The MES VIs will now have the typedefs from the TestConfig class on their connector panes, but at least the dependency is the correct "direction." Or, I can move the typedefs out of classes all together, but then I am not sure the best way to organize them. Looking for how others have handled these sorts of dependencies.
When I create new property node methods for a GOOP400 class using the OpenGDS they look like this :
The Write method gets the reference to the data and then modifies it in place.The read method gets a complete copy of the data and unbundles the wanted element. When the object contains a lot of other (large) elements I would like to avoid copying the entire data to unbundle just 1 element. This means also getting a DVR to the object and unbundle the element inside an in place element structure, as shown here :
In LabVIEW 2017 and above I could even use "Allow parallel read-only access." to make sure it's read-only.
Currently I modify such read methods manually each time I create a new one. I know I could update the template but I was wondering if there is any good reason not to do this. Or what is the reason why the original OpenGDS is reading by copying the entire cluster?
I need help regarding LVOOP implementation. I have gone through several examples and documents on LVOOP for quite some time, and finally decided to use it in this simple application. In my project LabVIEW application communicates between a PLC(local) and a server(TCP).I have used command pattern.For the server part i have created class and methods and it runs in a separate loop(i pass messages from main process loop). my problem is how can i make my main process using the same method? In QMH and state machine i can do it easily by checking condition and queuing next action how can i implement the same using OOP?
I have tried passing the next command in the current method. Is it the right way to do?
I am also thinking using a while loop inside methods for checking for validating conditions is it okay to do so?
Or should i use QMH for the main process to send commands to the server loop?
Or am i doing it all wrong?