AfraLISP - Learn AutoLISP for AutoCAD productivity

Properties & Methods - Part 2

by Kenny Ramage

How to Call a Visual Lisp Function

Right, you've identified the Visual Lisp Property or Method that you need, but you still need to determine how to call the function. You need to know the arguments to specify and the data type of those arguments. Let's look at Properties first.


The syntax for the Layer Property in VBA is as follows :

object.Layer or

object : All Drawing objects, AttributeRef, Group. The object or objects this property applies to.

Layer : String; read-write (write-only for the Group object). The name of the layer.


All entities have an associated layer. The document always contains at least one layer (layer 0). As with linetypes, you can specify a layer for an entity. If you don’t specify a layer, the current active layer is used for a new entity. If a layer is specified for an entity, the current active layer is ignored. Use the ActiveLayer property to set or query the current active layer. Each layer has associated properties that can be set and queried through the Layer object.

In VBA you would use :

Oldlayer = object.Layer to retrieve the Layer Name, and
object.Layer = "2"  to change the Layer Name.

Visual Lisp provides functions for reading and updating Object Properties. Functions that read Object Properties are named with a vla-get prefix and require the following syntax :

(vla-get-property object)

For example, vla-get-layer object returns the Layer the Object is on.

Enter this in the Visual Lisp Console :

_$ (vl-load-com)
_$ (setq acadDocument (vla-get-activedocument (vlax-get-acad-object)))
#<VLA-OBJECT IAcadDocument 00b94e14>

_$ (setq mspace (vla-get-modelspace acadDocument))
#<VLA-OBJECT IAcadModelSpace 01e42444>

_$ (setq apt (getpoint "Specify First Point: "))
(307.86 539.809 0.0)

_$ (setq pt (getpoint "Specify next point: " apt))
(738.188 479.426 0.0)

_$ (setq myline (vla-addline mspace (vlax-3d-point apt)
 (vlax-3d-point pt)))
#<VLA-OBJECT IAcadLine 01e81de4>

_$ (setq oldlayer (vla-get-layer myline))

The variable oldLayer now contains the Layer name of your Line Object.

Functions that update Properties are prefixed with vla-put and use the following syntax :

(vla-put-property object new-value)

For example, vla-put-layer object new-value changes the layer of the Object.

Enter this at the Console prompt :

_$ (vla-put-layer myline "4")

Your line will have now changed to Layer "4".


Let's have a look at Methods now. The syntax for the "Offset" Method in VBA is as follows :

RetVal = object.Offset(Distance) or Return Value = object.Method (arguments)

Object :  Arc, Circle, Ellipse, Line, LightweightPolyline, Polyline, Spline, XLine. The object or objects this method applies to. Distance :  Double; input-only. The distance to offset the object. The offset can be a positive or negative number, but it cannot equal zero. If the offset is negative, this is interpreted as being an offset to make a "smaller" curve (that is, for an arc it would offset to a radius that is "Distance less" than the starting curve's radius). If "smaller" has no meaning, then it would offset in the direction of smaller X, Y, and Z WCS coordinates.

RetVal : Variant (array of objects). An array of the newly created objects resulting from the offset.

In VBA you would use :
offsetObj = object.offset(15.5) to Offset an Object.

Syntax Definitions

The syntax definitions used in the "ActiveX and VBA Reference" were designed for Visual Basic Users. Consider the VBA Offset Method :

returnvalue = object.Method (arguments)
returnvalue = object.Offset(Distance) or using the names in our example
offLine = myline.Offset(15.5)

The syntax for the same operation in Visual Lisp is :

(setq returnvalue (vla-method object argument)) or using our names (setq offLine (vla-offset myline 15.5))

Different Objects have different Methods but the same principle applies.

Type this at the Console prompt :

_$ (setq offLine (vla-offset myline 15.5))
#<variant 8201 ...>

The variable offLine, now contains the data for your newly created line in the form of a variant array.


So to recap :

  • vla-get- functions correspond to every ActiveX Property, enabling you to retrieve the value of that Property (for example, vla-get-Color obtains an Object's Color Property.
  • vla-put- functions correspond to every Property, enabling you to update the value of the Property (for example, vla-put-Color updates an Objects Color Property.
  • vla- functions correspond to every ActiveX Method. Use these functions to invoke the Method (for example, vla-addCircle invokes the addCircle Method.

Visual Lisp also adds a set of ActiveX-related functions whose names are prefixed with vlax-. These are more general ActiveX functions, each of which can be applied to numerous Methods, Properties or Objects. For example, with the vlax-get-property function, you can obtain any Property of any ActiveX Object.

In Part 3 we'll have a look at how we can determine whether an Object is available for updating and whether a Method or a Property applies to an Object.