About Converting Object References (AutoLISP/ActiveX)

There are a number of ways to refer to AutoCAD drawing objects with AutoLISP. These include the following:

VLA-objects, returned by ActiveX functions
Entity names (enames), returned by entget and entsel, identifying objects in an open drawing
Handles, returned by handent, which entities retain across AutoCAD sessions
Object IDs, used by ARX to identify objects

AutoLISP provides functions to convert from one type of object identifier to another.

You may find the same drawing object represented by different identifiers and data types such as a handle string, an ename, a VLA-object, or an ObjectARX object ID integer. To obtain the identifier with the data type your program requires, use the following strategies:

To find the handle associated with an ename, use the DXF 5 group of the ename's association list:
```
(setq handle-circle (cdr (assoc 5 (entget ename-circle))))
"4F"
```
To find the ename associated with a handle, use the handent function:
```
(handent handle-circle)
<Entity name: 27f0538>
```

To find the VLA-object associated with a handle, use the vla-handleToObject function:

(setq vla-circle (vla-handleToObject acadDocument handle-circle))
#<VLA-OBJECT IAcadCircle 03642c24>

To find the handle associated with a VLA-object, use vla-get-handle to obtain the Handle property:
```
(vla-get-handle vla-circle)
"4F"
```
To find the ObjectARX object ID of a VLA-object, use vla-get-objectid to get the objectID property:
```
(setq objid-Circle (vla-get-objectid vla-circle))
41878840
```
To find the VLA-object identified by an ObjectARX object ID, use the ObjectID-toObject method on the AutoCAD Document object:
```
(vla-ObjectIDtoObject acadDocument objid-circle)
#<VLA-OBJECT IAcadCircle 03642c24>
```