The singleton design is one of the more commonly used
design patterns. Normally this requires quite a bit of code in every class.
Fortunately generics make this a lot easier and takes out almost all code
duplication.
Public
Class SingletonDemo
Public Sub
main()
' Using the singleton
TestClass.Instance.Write()
End Sub
End
Class
'''
<summary>
''' Generic singleton object wrapper.
'''
</summary>
'''
<typeparam
name="T"></typeparam>
'''
<remarks></remarks>
Public
Class SingletonProvider(Of
T As New)
Private Sub
New()
End Sub
Public
Shared ReadOnly
Property Instance() As T
Get
Return
SingletonCreator.instance
End Get
End Property
Class SingletonCreator
Shared Sub
New()
End Sub
Friend
Shared ReadOnly instance
As New T
End Class
End
Class
'''
<summary>
''' Test class for the singleton wrapper.
'''
</summary>
'''
<remarks></remarks>
Class TestClass
Private m_dt As
DateTime
Public Sub
New()
m_dt = DateTime.Now
End Sub
'''
<summary>
''' Test procedure.
'''
</summary>
'''
<remarks></remarks>
Public Sub
Write()
Console.WriteLine(m_dt.Ticks.ToString())
End Sub
'''
<summary>
''' Returning the singleton.
'''
</summary>
'''
<value></value>
'''
<returns></returns>
'''
<remarks></remarks>
Public
Shared ReadOnly
Property Instance() As TestClass
Get
Return SingletonProvider(Of
TestClass).Instance
End Get
End Property
End
Class
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