conditional logic based on "EntityType"

EvanReese

I'm basically trying to get a feature that says

if (my selection is a vertex)<br>{handle it one way}<br>else<br>{handle it another way}

I tried

if (definition.point == EntityType.VERTEX)

but it didn't like that. I'm new to this and I sense it's some mismatch of data types. How can I ask what EntityType a certain entity is? do I need to evaluate my query or something similar?

konstantin_shiriazdanov

There are no way to find entity type or geometry type until you try to evaluate it (which is not good i think), so:

try silent

{

var vertex = evVertex(selection)

//vertex handling code

}

try silent

{

var somethingElse = evSomethingElse(selection)

//some other specific code

}

ilya_baran

There are a few cases (like evAxis) when you currently need exception handling for flow control, but that's generally not the best way to do it.  try silent is especially dangerous, as you may miss real errors.

If I want to check if anything in myQuery resolves to a vertex, I would do:

if (evaluateQuery(context, qEntityFilter(myQuery, EntityType.VERTEX)) != [])
{
   ...
}

If I want to check the first thing my query resolves to (what evVertex would use), I'd put a qNthElement around myQuery also.

It's not too pretty, so if I found myself doing this frequently, I'd factor it out into a predicate.

konstantin_shiriazdanov

There are no way to find entity type or geometry type until you try to evaluate it (which is not good i think), so:

try silent

{

var vertex = evVertex(selection)

//vertex handling code

}

try silent

{

var somethingElse = evSomethingElse(selection)

//some other specific code

}

EvanReese

@konstantin_shiriazdanov
  
that worked! thanks. Didn't know about the try function. Let me make sure I understand it. It just tries something, and if there's an error, then it just ignores the code between the curly braces?

I searched the Standard Library Documentation and there is no use of the word "silent" there anywhere. Does that just make the try function not throw an error?

NeilCooke

You can also "catch" the try block which is especially useful if there are only 2 choices.

EvanReese

@NeilCooke
in my case there are only 2 choices (vertex or mate connector) so I'll have a look at that. Thanks.

konstantin_shiriazdanov

this operator is described in exception handling article: https://cad.onshape.com/FsDoc/exceptions.html

it exactly what you said - allows you to handle errors if you expect them during some code execution, in this case you should use such ev functions that the one and only correct evaluation should happen.

ilya_baran

There are a few cases (like evAxis) when you currently need exception handling for flow control, but that's generally not the best way to do it.  try silent is especially dangerous, as you may miss real errors.

If I want to check if anything in myQuery resolves to a vertex, I would do:

if (evaluateQuery(context, qEntityFilter(myQuery, EntityType.VERTEX)) != [])
{
   ...
}

If I want to check the first thing my query resolves to (what evVertex would use), I'd put a qNthElement around myQuery also.

It's not too pretty, so if I found myself doing this frequently, I'd factor it out into a predicate.

EvanReese

ilya_baran said:

There are a few cases (like evAxis) when you currently need exception handling for flow control, but that's generally not the best way to do it.  try silent is especially dangerous, as you may miss real errors.

If I want to check if anything in myQuery resolves to a vertex, I would do:

if (evaluateQuery(context, qEntityFilter(myQuery, EntityType.VERTEX)) != [])
{
   ...
}

If I want to check the first thing my query resolves to (what evVertex would use), I'd put a qNthElement around myQuery also.

It's not too pretty, so if I found myself doing this frequently, I'd factor it out into a predicate.

ooh! I like this way too. I'll add it to my toolkit. Thanks!