If a property or method is added to a class module, it becomes part of the class.
This property or method is usable by other modules in the same project as the class module. It is
also available to other projects, as a property or method of objects derived from that class.
This is the default setting for the scope of a property or method. There are three other ways
of defining the scope of a property or method:
Using the Public Keyword
If the Public keyword is used when defining a property or method, the property behaves
as though the Public keyword is not used. This is because the default scope of a property or
method defined in a class module is Public.
Public properties and methods are available to other modules in the same project
as the class module. They are also available to other projects as properties and methods of an
object derived from that class module. Most properties and methods will be defined as Public.
Consider the following, for example:
Public Property Get HireDate() as Date
Public Sub Save()
Using the Private Keyword
Using the Private keyword when defining a property or method creates a property
or method private to that class module. Only code in that class module can access the property or
method.
Private methods are typically support routines used by the properties of a class. For
example, you may need some helper routines that perform date calculations.
Consider the following, for example:
Private Function NextWorkDay(FromDate as Date) As Date
Private Sub PrintForm(FormName As String)
Using the Friend Keyword
Using the Friend keyword when defining a property or method creates a property or method
private to the project containing the class module. Code in the same class module as the procedure
can access the property or method. Code in other modules in the same project can also access the
property or method. This is useful when creating helper classes that should not be used by other
programs.
Friend properties and methods are often used when a number of classes assist the
main class that other programs will use. A class used to write another object to a file, for example,
might have two methods: Load and Save. These methods, declared as Friend, would allow the calling object
to access them. They would not be available to other projects.
Consider the following, for example:
Friend Sub Load(FileName As String)
Friend Function Save(FileName As String) As Boolean
By explicitly setting the scope for each of the properties and methods in a
class, you can better control how other modules and programs access them. Most
properties and methods will be Public; however, having access to the Private and
Friend keywords allows for greater control of access.
