COM Class

Article
04/11/2014

The COM class is use to create Component Object Model (COM) objects.

Syntax

class COM

Run On

Called

Methods

	Method	Description
	attach	Attaches an instance of the COM class to a COM interface.
	cancelTimeOut	Cancels a previous method call to the setTimeOut method. (Inherited from Object.)
	detach	Detaches a COM object from the class that it was associated with.
	dispatch	Reserved. Do not explicitly call this method.
	documentationName	Returns the textual name of the COM object that is associated with the instance of the COM class.
	equal	Determines whether the specified object is equal to the current one. (Inherited from Object.)
	error	Returns a COMError object that is associated with the instance of the COM class.
	finalize	Frees resources that are associated with the instance of the COM class.
	getTimeOutTimerHandle	Returns the timer handle for the object. (Inherited from Object.)
	handle	Retrieves the handle of the class of the object. (Inherited from Object.)
	interface	Returns the interface that is associated with the COM object.
	lcid
	new	Creates an instance of the COM class that can be attached to the COM class and optionally instantiates a COM object on a specified computer.
	notify	Releases the hold on an object that has called the wait method on this object. (Inherited from Object.)
	notifyAll	Releases a lock on the object that was issued by the wait method on this object. (Inherited from Object.)
	objectOnServer	Determines whether the object is on a server. (Inherited from Object.)
	owner	Returns the instance that owns the object. (Inherited from Object.)
	setTimeOut	Sets up the scheduled execution of a specified method. (Inherited from Object.)
	toString	Returns a string that represents the instance of the COM class.
	usageCount	Returns the current number of references, that is, the value of the reference counter, that the object has. (Inherited from Object.)
	wait	Pauses a process. (Inherited from Object.)
	xml	Returns an XML string that represents the current object. (Inherited from Object.)
	::createFromInterface	Creates an instance of the COM class by using the specified COM interface.
	::createFromObject	Creates an instance of the COM class by using the specified COM object.
	::createFromVariant	Creates an instance of the COM class by using the specified instance of the COMVariant class.
	::getObject	Returns an instance of a COM object that is running.
	::getObjectEx	Returns an instance of a COM object that is specified by its file name.
	::unsupported	Reserved.

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Remarks

The COM class also supports Distributed Component Object Model (DCOM). DCOM enables objects that support DCOM to run on remote computers.

When a COM object has been instantiated by using the COM class, its methods and properties can be accessed by using either the COMDispFunction class or the extended syntax for the COM class.

The extended syntax enables methods and properties to be directly called on the COM object, even though they don't appear in the Lookup list (for example, com.comMethod("Hello World");). The extended syntax supports calls to methods and properties that take any number of arguments.

Some COM objects support the concept of optional arguments. Only optional variant arguments can be omitted. If optional arguments are omitted, the COM object uses its default values. To omit an argument for the COM object and force it to use its default value, specify the COMArgument::NoValue enumeration, as shown in the following example.

com.comMethod(COMArgument::NoValue, "Hello Another World");

If the arguments to omit from the COM object appear at the end of the argument list, omit them from the code.

The following types are supported for the extended syntax for the COM class argument type and return type:

array
COM
COMVariant
date
enum
int
real
str

If a COM object returns a date, and if the extended syntax is used, the return value of the COM method should be assigned to a COMVariant class variable. The actual date and time (format) can then be extracted from the COMVariant class by using the date and time properties. If the date return value is assigned to a date variable instead of a COMVariant class, the time component of the date is lost.

When the extended syntax is used, you can still call the COM class methods (the methods that appear in the Lookup list) on the objects. The COM class methods have a higher priority than the methods on the actual COM object.

If a method on the COM object has the same name as a method on the COM class (for example, attach), you cannot call that method on the COM object. To enable Microsoft Dynamics AX to call the method on the COM object instead of the method that has the same name on the COM class, prefix the duplicate method name with an underscore (for example, com._detach();).

The extended syntax for the COM class is evaluated at run time, not compile time, which causes a slight decrease in performance. If high-performance code is required, consider using the COMDispFunction class. This class offers performance improvements over the extended syntax for the COM class.

Examples

This example calls the GetFileName method from the Scripting.FileSystemObject COM object.

void COMExample() 
{ 
    COM               com; 
    str               result; 
    InteropPermission perm; 
    ; 
  
    // Set code access permission to help protect the use of the 
    // COM object. 
    perm = new InteropPermission(InteropKind::ComInterop); 
    if (perm == null) 
    { 
        return; 
    } 
    // Permission scope starts here. 
    perm.assert(); 
  
    com = new COM("Scripting.FileSystemObject"); 
    if (com != null) 
    { 
        result = com.GetFileName(@"c:\boot.ini"); 
    } 
  
    // Close code access permission scope. 
    CodeAccessPermission::revertAssert(); 
}

Inheritance Hierarchy

Object Class
COM Class
SysCOM Class

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