How to detect an empty Variant?

[altenbach]

Also remember that an empty variant can still have variant attributes that can differ.

[BowenM]

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@GerdW wrote:

Hi PNB,

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@PNB wrote:

If the variant e.g. contains 64byte integer values, this comparison will also result in true, although data are contained within the variant.

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Can you please provide an example VI to demonstrate that observation?

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The only instance I could see of this method not working is if your incoming variant is "empty", but has variant attributes.

In that case you'd probably need to use "Get Type Information" to tell if the variant itself is empty.

[d.w.b · Accepted solution]

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@PNB wrote:

Is there a universal method to detect empty variants...?

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Yes, the Empty String/Path? Function on the Comparison Functions Palette "is also designed to work with variants, pictures, and DSC tags." -- https://www.ni.com/docs/en-US/bundle/labview/page/glang/empty_string_path.html

To make this easier to find Kudo the idea to put it on the Variant Palette -- https://forums.ni.com/t5/LabVIEW-Idea-Exchange/Empty-Variant-Function-To-Variant-Palette/idi-p/42818...

[wiebe@CARYA]

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@d.w.b wrote:

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@PNB wrote:

Is there a universal method to detect empty variants...?

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Yes, the Empty String/Path? Function on the Comparison Functions Palette "is also designed to work with variants, pictures, and DSC tags." -- https://www.ni.com/docs/en-US/bundle/labview/page/glang/empty_string_path.html

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Nice, didn't know that. It's tricky though:

So Empty String/Path is false if the empty string/Path is converted to a variant first... 

[Hooovahh]

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wiebe@CARYA wrote:

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Nice, didn't know that. It's tricky though:

So Empty String/Path is false if the empty string/Path is converted to a variant first... 

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That seems logical to me.  The variant isn't empty, it contains a string.  That string just happens to be a null, but the variant does contain that null.  But I could see the confusion if people aren't aware that it works this way.

[wiebe@CARYA]

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@Hooovahh wrote:

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wiebe@CARYA wrote:

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Nice, didn't know that. It's tricky though:

So Empty String/Path is false if the empty string/Path is converted to a variant first... 

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That seems logical to me.  The variant isn't empty, it contains a string.  That string just happens to be a null, but the variant does contain that null.  But I could see the confusion if people aren't aware that it works this way.

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I think it's something I'll double check every time I'm going to use it. Maybe someday I'll remember.

But, a lot better then getting the type and checking if it's null.