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The reason for this typecast is to break type propagation that plagues edit-time performance which occur when you have a large class hierarchy. It is not because it makes scripting easier (on the contrary). In essence, when you edit a class' private member, the class' mutation history is modified and the LabVIEW IDE goes through a series of checks and recompiles to propagate the changes. For very small projects, this is completely trivial and does not affect edit-time performance, but for larger hierarchies (think Actor framework...) it becomes a real issue. One way to reduce this performance lag is to never put typedefs in the class private data... but this is up to the developer to stick to that rule or not. When you use an integer, using typedefs does not affect the edit time performances at all. As Rolf mentions, this pattern was popularized by GOOP (now OpenGDS). When creating a framework, you can never predict how the developers will use it... Obviously, if you use a framework and it starts to lag as your project's complexity increases, you are quickly going to blame the framework for the performance degradation (just like we blame Windows for running slower after we've bloated our computers with a bunch of apps, but that's another topic...). So it is very tempting to use tricks like this typecast to an integer to break this slow type propagation. As was mentioned by Smithd, it is risky... but if it stays in the private methods of your class, it is totally safe. In JKI SMO, you'll notice that this is used through two private methods and the DVR type is typedef'ed. You can very well create SMOs that do not use this trick.

It does not crash if you typecast the integer to the right refnum (be it DVR or any other LabVIEW refnum), But it can badly crash if you ever convert DVR_A into an int and then try to convert it back into DVR_B or any other LabVIEW refnum. The int typecast removes any type safety and LabVIEW has no foolproof way to detect in the Typecast to Refnum conversion that everything is alright. LabVIEW does have some safety built in there such that part of the uint32 value of any refnum is reserved as a random identifier for the refnum type pool it resides in (so a file refnum has another bit pattern for those bits than a network refnum) but it can not verify safely that the int coming from a DVR_X is fully compatible to the DVR_Y you want to convert it to. And then as soon as it attempts to access the internals from DVR_Y according to its datatype it badly reaches into nirvana. So if you do the typecasting all safely behind the private interface of a class so that nobody else can ever meddle with it AND you are very very careful when developing your class to never ever typecast the wrong integer into a specific DVR (or Queue, Notifier, Semaphore, etc) you are fine, but there is no LabVIEW holding your hand here to prevent you from shooting in your own feet! The original idea comes from before there where DVRs and LabVIEW GOOP. In LabVIEW 6 or 7 someone developed a first version of LVOOP, which used a private "refnum" repository implemented in the LabVIEW kernel and accessed through private VIs using a Call Library Node. It was basically like a DVR that was also the class wire. Obvriously DD was not something that would work seemlessly but had to be programmed explicitedly by the class developer and hence was seldom used. The pointer (which was back then an int32 since all LabVIEW versions were 32 bit only) was then typecast into a datalog file refnum with a specific enum type for typesafety so that you had a typesafe refnum wire to carry around as class wire. Some of the DVR based class design (reference based classes) in the Endevo/NI GOOP Framework still reminds of this original idea, but now using proper LabVIEW classes as the class wire. Additional bonus is that this buys them automatic dynamic dispatch capability.