LabVIEW Idea Exchange

I propose a property node to tell if a control was wired when This VI was called as a subVI.

Sometimes it is practical to be able to distinguish if the value in a control was wired to it (data arrived via dataflow), or if the control was unwired and the value hence the control's default value. Even comparison with the known default value of the control isn't enough, as the program logic may depend on the value source.

Consider an FG that stores two data elements:

You'll have to have two Set functions for this, one for Data 1 ("Set data 1"), and one for Data 2 ("Set data 2"). If you have only one Set function, you add the constraint that both data sets have to be present (wired) every time you set any of the two data sets, or else the unwired set will get overwritten in the FG with the default value of the unwired control. If the FG could decide programmatically if the value was wired to the control, or if it was merely the default value of the unwired control, it could decide whether to overwrite its stored copy or not. The data values could be the same in the two cases, but the actions very different. This is just a simple example, but I have many much more complex cases, that would get much simpler if I could tell where the control value came from. In the above example you could even dispose of the Function input alltogether, if I could tell if any data inputs were wired.

A polymorphic VI will remedy some of these issues, but not all, and in other cases a polymorphic VI is a drastic solution to a simple problem. It's also not an issue in a Top-level VI, as such run only once (only subVIs get called again and again, while depending on prior runs).

A new feature that would act similarly to the "Automatically close VISA sessions" option and close all open file references once the top level VI has stopped running.

This new function would preclude the situation where LabVIEW locks, and keeps a file locked until the entire development environment is closed.

(I would even be happy with a menu option to explicitly close all open file references.)

The primary use case would be during development/debugging. If you stop or abort your top level VI without closing a file reference, LabVIEW will hang on to the reference keeping it open, but inacessable, until the dev environment is shut down.

It seems that if there is not an open reference to the file on the block diagram or the top level VI has stopped running, and certainly when all open VIs are closed, then all files should be closed and locking handles should be released.

I suppose this concept could be expanded to cover any reference type that LabVIEW does not implicitly close when the top level vi goes idle.