Using Express VIs

[PaulG.]

I've been using LV for over 10 years and I use the occasional express VI. But I also rely heavily on OpenG and code reuse libraries as well. If an express VI will do what I want what's the sense in creating it from scratch? No sense reinventing the wheel. It's a waste of time.

[DianeS]

I see Paul's point, but I would say this:  Paul, as you say, you've been programming in LabVIEW for >10years.  You understand what's going on inside that Express VI.  So the use of the occasional Express VI makes sense in your case.  You understand what your code is doing.  If it behaves oddly, or vomits, you can figure out why and fix it.

I believe that the vast majority of users of Express VIs are beginners.  They don't know LabVIEW, and to them, the Express VI is a "black box" that magically performs their tasks with no effort or understanding on their part.  If they run into problems, they're at a loss.  I've certainly seen that repeatedly on this forum.  

I would not use someone else's code in one of my applications unless I understood what it was doing and how.  I doubt that you would either.  (maybe I'm wrong?  if I send you some LV code that does a bunch of cool stuff, but prevent you from seeing the block diagram, would you really deploy it in one of your own applications?  )  The original poster was asking if the Express VIs are a good learning tool, and I would argue that they are not. 

I'm not saying they don't have their place.  I'm saying that, if you are trying to learn LabVIEW, the sample programs are a much better bet.  The key difference here is whether understanding already exists or not, and too often it doesn't.

[PaulG.]

Indeed, example programs are much better. But I disagree that express VI's are not a good learning tool. I have learned a lot about LV with the express VI's. Once it's working the way I want it to I can open the front panel then look into the block diagram to see how it works. It's there where I can see all the nuts and bolts ... and superflous garbage ... as a beginner. Heck, even after 10 years in many ways I'm still a beginner.

[andre.buurman@carya]

Together with Express VI came the Dynamic data wires. They are somewhat required when using Express VI's, but have a very nasty side effect. They tend to hide the real data type travelling the wire. I once had some code rewriting to do for a customer that used Express VI's extensively. When looking at the diagram all I saw were those purple wires. A double going into a compare comes out as boolean, but not with those purple ones, they stay purple. So making it difficult to see bigger picture in the blink of an eye, as wouldn't be a problem when the basic data type were used.

I try to keep anything with dynamic data wires at a distance, therefor only a few Express VI's (E.g. "Time delay", "File Dialog") would make it to my code.

[Coq_Rouge]

In my Labview class, the use of express VIs is banned. A student report will not pass if express VIs are used. Perhaps some people will find this to harsh. But in my opinion the use of express VIs will only work against the process of learning Labview. You can not learn Labview by tossing out some express VIs on a block diagram, in a happy-go-lucky style. On the other hand I encourage my students to use the find example function frequently. An I also learn my students how they may use the express VIs as a source for inspiration. If they find some useful code in an express VI. They are welcome to use it. But they must document the functionality on the same level as the rest of the code they use

[NitzZ]

Hi,

Can anyone direct me to a link where i can get some deep knowledge about express VIs. The basic concepts, its components and the Do's and Dont's of it.

Regards,

Nitzz 

[Coq_Rouge]

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@NitzZ wrote:

Hi,

Can anyone direct me to a link where i can get some deep knowledge about express VIs. The basic concepts, its components and the Do's and Dont's of it.

Regards,

Nitzz 

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The Express VI concept is just some flimflams that NI have glued on top on Labview using very cheap glue. You will far better of standard Labview. Most of the Express VIs are coded in a quite ineffective coding style. And the dynamic data type that appears as a dark blue terminal. What a pain DoH! So the Do's are do not use them. Some of the Express VIs may show glimps of good programming ideas. In that case. Convert the Express VI to a standard VI. Open it and strip away all the extra weight not not needed. Then save it as a standard VI. I guess you have read all the postings in this thread. None of them do not directly applaud the Express VI concept. So why do you want to use them.

[NitzZ]

Hi  Coq Rouge,

Yeah, I have gone through all the replies in this thread and none of them have suggested to use Express VIs. Well, I didn't have any plans to use it in my code either.:) I was just curious about its concept and so wanted to know more about it.. Anyway, now i'll just try to keep some distance from all these express VIs.. All these posts have made Express VIs look scary to me So even I'm saying no to them..:)

anyway, thanks for your kind response.

Regards,

Nitzz