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I've been working a lot lately with by-reference architectures that still cooperate completely with LabVIEW's implementation of OOP and polymorphism. I've also recently taken an interest in trying to speed up development with secondary providers (similar to GOOP) to enable automatic creation of accessor VIs hidden behind the DVR, automatic creation of the private data type and constructor/destructor, etc. within the project window. I'm generally not a fan of the extra stuff that goop adds in to classes, I'd prefer to keep the source code looking as close to a normal class as possible. That said, I've started on my first ever XNode and it's a cross between an unbundle by name node and the -> operator in C. It functions just like a normal UBN, however it was also pull items out of DVRs. Having to plop down a UBN to pull out the reference from the class, an in place node to dereference, and then another UBN to pull the data out gets tiresome after about the 100th property VI gets written. So far I've gotten the node drawing completed (except for data type coloring of the labels), the type inferencing from the input wire, and the popup menu for selecting an item. Next up will be the menu selection code so that the names will finally show up in the terminals! Then I get the daunting task of scripting up the GenerateCode ability >_> Anyone interested in something like this? Following this will be a match to the Bundle by Name node that serves the same purpose except to write the items.
Hi, I would like to play an idea out to you about having a composite class put itself back in its owning object by a DVR. Is that a good or a terrible idea? Background I need a class that represents some different LabVIEW files, and which can offer some operations on those files; LVFile.lvclass. LVFile.lvclass has some children (LV file types) and it owns a composite object LVFileRefs.lvclass: LVFileRefs LVFileRefs contains the following: - An enum stating the file type. - A reference to the LabVIEW file (class reference, library reference, project reference, or VI reference). - The path to the file on disk (if it is saved to disk). - Info if the refnum was created by the object or passed in from the outside (used by the Close method). I need LVFileRefs as a composite object (instead of that data living inside LVFile) since New starts by instantiating an LVFileRefs object before New can decide which child to instantiate: One of the responsibilities of LVFileRefs is to keep disk path and file reference synchronized. This means that you could start out with a VI in memory for instance, and create an LVFile object for that. This does not yet have a File Path. If you then save that VI, then LVFileRefs will update its internal File Path field from <Not-A-Path> to the proper path. If for whichever reason the original file refnum goes stale, LVFileRefs will also be able to open a new refnum from File Path if possible. All transparent to the user. So LVFileRefs maintains a firm grip of the file whether it being in memory only or on disk, and it can tell you which type it is (some types take more programming to tell apart than others, and type can change as well). All stuff that makes writing apps that handle many different file types simpler. No DVR approach Normally I wouldn't expose a naked refnum to the user, but one of the features of LVFile is actually to serve the proper refnum, so in this case I do. That is currently done with accessors on LVFile, and then an LVFileRef method: Since LVFileRefs can update its embedded refnum it is important to write the LVFileRefs object back into the owning LVFile object (or else Close for instance wouldn't close the correct refnum, and several other issues). DVR approach Having to write back the LVFileRefs object is error prone - the user could forget to do it, and having to do it in the first place is irritating. I'd rather you could omit the write back step: The idea is to have LVFile embed a DVR to itself inside its LVFileRefs object, with which LVFileRefs can write itself back into its owning LVFile object with whenever LVFileRefs has updated itself. There shouldn't be any racing possible, as LVFileRefs is actually the representation of the LV file, and DVR access is mutexed. Am I insane considering this? Cheers, Steen
I'm in the systems engineering group at NI. Over the course of the past year(s), we've received feedback (most recently here -- sorry, this link is in the ni.com/community CLA group so access may be restricted) that some members of the community would be interested in contributing to some of the projects we've already released, or potentially working with us to identify future projects that might benefit the community at large. We'd like to renew this conversation by opening up a discussion of what projects might interest the community. That discussion is posted here: https://decibel.ni.com/content/thread/23441 If you have any thoughts or feedback, feel free to post here or in that discussion. We're very interested in hearing from you.