Scan from string error

[psilviu]

    Hi,

    I have a problem with "Scan from string" when at its input is there an empty string. But not in every cases: if it is an empty string constant is ok, but when it's an output of "Index Array" bloc/function, is not. See the attachments bellow containing both cases. Is it a bug? Do I miss something?

    Tnx
    Silviu

 

[Norbert_B]

Silviu,

the issue is created by the way you are working with the string/enums.
In the screenshot which shows the error, you retrieve the strings of the enum, retrieve an empty string using -1 as index and then look in this empty string for an value defined in the enum.
The screenshot without any error, you pass an empty string directly in the search function.

Where is the exact difference?
I cannor tell you exactly, WHY LV makes a difference here, but if you don't read the strings from the enum using the property node, it will work.

hope this helps,
Norbert

[smercurio_fc]

What version of LabVIEW are you using? Under 8.2 I get an error either way.

[psilviu]

" What version of LabVIEW are you using? Under 8.2 I get an error either way. "
So I should condider myself lucky? 🙂 I use version 8.5. So it's normal to get that error?!

[smercurio_fc]

In my opinion, you should get the error in either case, not just in one, since the input to the Scan From String function is the same.

[psilviu]

Why? I do have a default value at the input of the bloc.

LabView Help: "If this function cannot scan the input value from format string, the function uses the default."

So?!

[tst]

The function is operating correctly.

For one thing it does output the default value, but since you don't have a wire coming out of it, you can't see that.

For another, it does throw the same error in both cases (I see this in 8.5.1).
You're almost definitely not seeing this error because you have automatic error handling turned off in the second case, either in the Options dialog or for the VI itself. If you add an error indicator, you should see it.

In any case, you should note that it does not say that the function will not throw an error if it cannot find the string, just that the output will have the default value (because it has to have some value).

[psilviu]

Yes, I know that the block output the default value in both cases and yes, I know that "error out" output an error in both cases, too.
But in one case only that error window appears and this is my problem. The "error out" I could simply not connect and consequently ignore, but the appearance of that error window stops the normal flow of my vi.

[tst]

As I mentioned, that's called automatic error handling - if you don't wire an error terminal and an error occurs, LabVIEW throws an error dialog. You can disable this in the options dialog or in the properties for this specific VI (in the Execution page), but I personally think you shouldn't turn it off and just wire the error out. You can read more about it here.

[smercurio_fc]

Oh, you were talking about the error dialog, not the error cluster. That's definitely different.