TDMS Oddity

[jyoung8711]

So, I was working on a project today, and came across this little (seeming) oddity while trying to read from a TDMS file.

For the current application, I'm moving around Group/Channel pairs in a single string with a (:) delimiter... So essentially a string which says "Group:Channel" . When I want to read / write this channel, I figured I'd just pass it through a match pattern VI, and pass the two substrings into the "Read TDMS.vi"

Well... surprisingly this doesn't seem to be allowed.  It creates a broken arrow on the "Channel" input wire, saying that the types "String" and "(Sub)String" don't match.

This does not happen for the "Match Regular Expression" VI, and a seeming workaround is to just put in a "Type Cast" block...  See attached snippet.

I might be missing something here, but this seems to be an error of some sort.  This behavior occurs in both 2015 & 2017 (32-bit).  Snippet is 2017,

[Ben]

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@jyoung8711 wrote:

...

Well... surprisingly this doesn't seem to be allowed.  It creates a broken arrow on the "Channel" input wire, saying that the types "String" and "(Sub)String" don't match.

This does not happen for the "Match Regular Expression" VI, and a seeming workaround is to just put in a "Type Cast" block...  See attached snippet.

I might be missing something here, but this seems to be an error of some sort.  This behavior occurs in both 2015 & 2017 (32-bit).  Snippet is 2017,

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That smell like a bug.

 The type-cast is probably a valid work-around

Spoiler

Generally should be used with cautions since it assumes that we know what we are doing when we use it. Been there done that... wrong! Once had an issue with LV crashing that had to go to R&D to discover I was type casting an array of class instances as a single instance of a class.

Ben

[Hooovahh]

I'm betting an always copy will fix this too.

[mcduff]

@Hooovahh

You are right, always copy works.

So does Concatenate.

mcduff

[jyoung8711]

Thanks for the feedback! I'll go ahead and submit this as a bug.

I like the both of the workarounds posted here more than the type cast.  I only really use that function when it's absolutely necessary... I don't feel that I always know what it's doing, and sometimes the results catch me off guard.