Visual Basic 2005 in a Nutshell, Third Edition

OOP Development in Visual Basic | 33

OOP

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

Overloads keyword—described later in this chapter—must be added to each

declaration. However the

New procedure is a special case; it does not require the

Overloads keyword.)

For classes that require no special initialization of their public or private members,

the constructor can be omitted from the class; Visual Basic will provide a default

constructor when no defined constructor exists in a class. But many classes

require some basic initialization, and the constructor is the place to do it. The

Person class defined earlier includes two constructors.

Public Sub New( )

' ----- Default constructor.

fullName = "<unnamed>"

End Sub

Public Sub New(ByVal newName As String)

' ----- Simple constructor to set an initial field.

fullName = newName

End Sub

The first constructor is the default constructor; since it includes no arguments in

its declaration signature, it is used by default when an instance is created that

lacks any initialization arguments. The second constructor is a custom constructor;

it is called when an instance is created that passes a single string argument.

' ----- Uses the default constructor.

Dim byDefault As Person = New Person

' ----- Uses the custom constructor.

Dim byCustom As Person = New Person("John Q. Public")

The arguments