How can I verify an ObjectId is valid in a drawing?

/snip

'Find an object from a given objectID
Set tempObj = ThisDrawing.ObjectIdToObject(newObjsString)
/snip

This is a line I have in my code, it works great if the ObjectId is valid,
but if it is not, AutoCAD creates a Fatal Error, and crashes.

If I have a ObjectId number, how can verify it is valid without AutoCAD
crashing?

Thanks again all,
Dan

 

Are you using an "On Error Goto" construct?

 

Yes I am: On Error GoTo Err_Control
Dan

 

Why are you trying to determine if an ObjectID is valid? Are you storing the
ObjectID in a database for later retrieval? ObjectIDs are transient and not
persistent between drawing loads. I can look into how to do this but first I
want to make sure you aren't trying to do something you should not be doing.

Handles are persistent between drawing loads btw.

Cheers,

Jorge

 

AutoCAD shouldn't crash if you give ObjectIDToObject() an invalid
object id. But, your code below suggests you're passing a string
into the method. Are you?

Why would you need to verify if an object id is valid? If an object
is erased (or unappeneded), its object id is still valid, but this
method will generate an error nontheless.

Step back and tell us what the purpose of validating the object id is.

 

Thanks for the assistance....
The purpose is to create a Field mapping tool.

Purpose is simply this:

There is a defined field that needs to be modified.
How does the user know where the parent of that field resides?

Solution/Tool

I have written some code to prompt the user to select desired field, then
the code reads the field expression,
then zooms to the Objectid in the expression and highlights it for the user,
for the user to make necessary modifications.


Odd thing as stated in a previous post, it works great, but there is some
anomily that can give the wrong objectid.
(See "What's wrong in code? Get Field Expression Tool thread")

If Objectid provided is not a valid ID, AutoCAD will crash when I get to
this line:
Set tempObj = ThisDrawing.ObjectIdToObject(newObjsString)

Thanks,
Dan

:

 

Per chance, are you using object ids that have small values?

This is a known problem. In some cases, the object referenced
by the object id is valid, but has no COM/ActiveX representation
or wrapper object, and I'm pretty sure that this may cause
the crash.

 

still no ideas....?