After you've set a reference to a COM component in your application, you
can instantiate objects from the component's classes in your application.
You may declare an object variable for a component class that you want to use.
You can then use this object variable to point to an instance of the corresponding class.
The New keyword is Microsoft's preferred technique for instantiating object
variables from server classes. You can use the New keyword in one of two ways, discussed in
the following sections:
Many COM components don't support the New keyword. Refer to each component's
documentation to see whether it supports New. If the component you want to use doesn't
support New, you will need to use the CreateObject or GetObject function, as discussed in the section
of this chapter entitled "Using the CreateObject and GetObject Functions to Instantiate Objects."
NOTE - VB Version Support for the New Keyword: Components
created in VB4, VB5, or VB6 always support the New keyword. See Chapters
12, 13, and 14
for a discussion of how to create ActiveX components in VB6.
Using As New to Instantiate an Object Variable When You Declare It
If the component whose class you want to instantiate supports the New keyword,
all you need to do is declare a variable of appropriate scope (usually Private or Public),
and the object is ready to use in your application. For example, if you want to use a class called
MyClass from a component application called MyComp, your variable declaration in a General
Declarations section might look like this:
Private objMyClass As New MyComp.MyClass
You could then manipulate the object's methods and properties and react
to its events through your own application's code.
Using New to Instantiate an Object Variable After You Declare It
In the previous section, an object variable was instantiated at the same time it
was declared. If you wanted to manage your object more tightly, you could wait until you actually
needed to use the variable before instantiating it.
It's possible to declare an object variable without instantiating it and then instantiate it as needed with a combination
of the Set statement and the New keyword, as illustrated in Listing 10.1.
LISTING 10.1INSTANTIATING AN OBJECT VARIABLE WITH THE New KEYWORD
AFTER YOU HAVE DECLARED IT
Private objMyClass As MyComp.MyClass
'later in your code
Set objMyClass = New Mycomp.MyClass
This second method, as illustrated in Listing 10.1, is preferred over the method
of the previous section (declaring the variable with As New). The As New declaration
requires extra runtime checking of the variable type.