User Guide

370 Chapter 20 Using cfobject to Invoke Component Objects

Calling nested objects

The current release of ColdFusion does not support nested (scoped) object calls. For

example, if an object method returns another object and you must invoke a property

or method on that object, use the following syntax:

(The syntax <cfset prop = myObj.X.Property> fails.)

Getting Started with COM/DCOM

ColdFusion is an automation (late-binding) COM client. As a result, the COM object

must support the IDispatch interface, and arguments for methods and properties

must be standard automation types. Because ColdFusion is a typeless language, it

uses the object’s type information to correctly set up the arguments on call

invocations. Any ambiguity in the object’s data types can lead to unexpected

behavior.

In ColdFusion, you should only use server-side COM objects, which do not have a

graphical user interface. If your ColdFusion application invokes an object with a

graphical interface in a window, the component might appear on the Web server

desktop, not on the user’s desktop. This can take up ColdFusion Server threads and

result in further Web server requests not being serviced.

ColdFusion can call Inproc, Local, or Remote COM objects. The attributes specified

in the

cfobject tag determine which type of object is called.

Requirements for COM

To make use of COM components in your ColdFusion application, you need at least

the following items:

• Microsoft OLE/COM Object Viewer, available from Microsoft at http://

www.microsoft.com/com/resources/oleview.asp. This tool is handy for viewing

registered COM objects.

• The COM objects, which are typically DLL or EXE files, that you want to use in

your ColdFusion application pages. These components should allow late

binding, that is, they should implement the IDispatch interface. Object Viewer

lets you view an object’s class information so that you can properly define the

class attribute for the cfobject tag. It also displays the object’s supported

interfaces, so you can discover the properties and methods (for the IDispatch

interface) of the object.