Query that Resolves to nothing != qNothing()

Jonathan_Hutchinson

I stumbled on some strange behaviour I couldn't figure out. What I thought was quite a straightforward conditional where I do a qSubtraction, resolved weirdly. As below.

                const allGeom = qCreatedBy(id + "extrudeThin", EntityType.FACE);

                const planeGeom = qGeometry(qCreatedBy(id + "extrudeThin", EntityType.FACE), GeometryType.PLANE);

                const curvedGeom = qSubtraction(allGeom, planeGeom);

                debug(context, allGeom, DebugColor.RED);

                debug(context, planeGeom, DebugColor.RED);

                debug(context, curvedGeom, DebugColor.RED);

                if (curvedGeom != qNothing())

                {

                    println("is something");

                }

                else

                {

                    println("is nothing");

                }

Returned in the console:

debug: Query resolves to 6 faces
debug: Query resolves to 6 faces
debug: Query resolves to nothing >>> (curvedGeom variable)
is something >>> (curvedGeom variable, resolves to nothing but isn't equal to qNothing?)

My workaround is to evaluate the query and test if it's equal to an empty array. But I thought equality to qNothing was possible?

Jacob_Corder

qNothing is a query structure and is only the same as another qNothing(). An empty query will not resolve to qNothing() it will return [] from evaluateQuery and false with isQueryEmpty. To solve your current code, the fastest ways is
if(isQueryEmpty(curvedGeom)==false)
{

}

so, use isQueryEmpty(curvedGeom)

Jonathan_Hutchinson

Ah, thank you! I don't know why I had it in my head that comparing to a qNothing would help me out.

NeilCooke

Or, even more succinct:

if(!isQueryEmpty(curvedGeom))
{

}