How to find if a dictionary exists

I am working on a lisp routine to modify a layer state, but I need to verify
the ACAD_LAYERSTATES dictionary exists in the drawing first. I can't figure
out how to search for a dictionary without getting an error at the command
line. A new drawing doesn't contain this dictionary until a layer state is
saved.

Tom

 

Tom,

Use member or vl-position...

;returns: a list of dictionary names
(defun ListDictionaries ( / dicts lst )
(setq dicts
(vla-get-dictionaries
(vla-get-activedocument
(vlax-get-acad-object))))
(vlax-for x dicts
(if (vlax-property-available-p x 'Name)
(setq lst (cons (vlax-get x 'Name) lst))
)
)
) ;end

Joe Burke

 

Hi Joe,

I thought about trying to answer this question but
with all the different ways layer states are stored
these days (lman, views, layer manager) I was a
bit unsure as to which the OP needs and also how
each method differs in storage/retrieval.

I don't think the layer states dictionary is accessible
with the method you demonstrated, at least not with
the quick tests I did this afternoon after initially
reading this thread. Perhaps you know differently?

Also, regarding your sample code, testing for the
existence of a single object within a collection I'd
use vla-item instead of vlax-for. (assuming that is
the OP's actual requirements)

On an additional note, have you run into times where
a dictionary doesn't have a name property? Just
curious about your use of vlax-property-available-p
in this case.

(feeling long-winded)

 

Jason,
If you (vlax-for through the dictionary collection, the very first item in
the collection is the Groups collection. I have no idea why it is a part of
the Dictionaries, but it does not have a Name property and will cause any
function to fail that tries to list it.

; IAcadGroups: The collection of all groups in the drawing
; Property values:
; Application (RO) = #<VLA-OBJECT IAcadApplication 00a8a730>
; Count (RO) = 0
; Document (RO) = #<VLA-OBJECT IAcadDocument 0104b71c>
; Handle (RO) = "D"
; HasExtensionDictionary (RO) = 0
; ObjectID (RO) = 1074277480
; ObjectName (RO) = "AcDbDictionary"
; OwnerID (RO) = 1074277472

Jeff

 

Hi Jason,

You guessed it. I'm clueless regarding layer states. In a sense, I took Tom's
question at face value.

Agreed, the item method is more direct when you know an object can be retrieved, or
checked for, that way. But I was aware not all dictionaries return a name. Which
seems strange given the "named object dictionary". That's why the property available
check.

So my thought was provide a list of all available dictionary names. Then see where
things went from there.

Besides what Jeff mentioned, the ACAD_LAYOUT and ACAD_PLOTSETTINGS dictionaries also
don't return a name.

Joe Burke

 

Jeff, Joe,

Thanks for pointing out the lack of a name property
on some dictionary objects. Funny I glanced at my
toolbox functions for dictionaries this morning, and
guess what? (vlax-property-available-p) is used
when grabbing the names. Guess I just forgot

 

Jason,

If I could remember everything I once knew... I'd be a freaking genius.

Pushing 55, it gets harder every day. Though I don't find that to be particularly
discouraging. Just another challenge, similar to learning in the first place.

Joe