How to detect an empty parameter?

I need to detect whether a parameter (a point, in this case) is empty or not. Something like an "IsEmpty" component that returns a boolean.

There's probably some obvious way to do this, but I just can't see it this morning :-)

Thanks for any help.

Replies to This Discussion

Permalink Reply by Daniel González Abalde on May 8, 2015 at 11:02am

If (x = Nothing) Then

(...)

end if

Permalink Reply by David Rutten on May 8, 2015 at 11:15am

Can you give us some more details? Do you want to know whether a parameter contains no data, whether the data you can get through DA.GetData is null, whether the data you can get through DA.GetData doesn't exist, ...?

Permalink Reply by Dave Johnson on May 8, 2015 at 11:25am

Sorry, here's a little more:

I'm writing a tool that will do some modifications on a surface only if a certain point component is "populated". So I want to somehow generate a boolean that tells me whether that point component is empty (orange) or not.

I was hoping there's a way to do this without scripting, though I'm happy to write a little C# thingie to do it.

Did that help?

Permalink Reply by Daniel González Abalde on May 8, 2015 at 11:44am

Null Item component

Permalink Reply by Dave Johnson on May 8, 2015 at 11:48am

Ah! That's exactly what I was looking for, thanks, Daniel! I knew it was there somewhere...

Permalink Reply by Dave Johnson on May 8, 2015 at 11:43am

A little sleuthing in C# shows me that an empty point component fed into a C# component ends up as the origin (0,0,0). So I can write something like:

if (x == Point3d.Origin)
A = false;
else
A = true;

And that will do the trick. (Of course, in the unlikely event that the user happens to pick the origin, I'd be in trouble...)

I'd still like to know if there's a way to do this with standard components, though. And/or a script that would work with ANY data type, not just points.

Permalink Reply by David Rutten on May 8, 2015 at 12:29pm

Well that's a problem, Point3d is a value type, so it cannot be null. Whenever I assign a null value to a Point3d field, it gets the default value which is (0,0,0). So it is not possible to detect whether a Point3d parameter has been assigned.

If you really need to check the data, you can look at the VolatileData of the parameter in question to see if the count is zero.

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