TIP: The Singleton Pattern

Singletons are very nifty. They are objects that can only exist once in memory. I like to use them when I create programs that deal with threading. They are the perfect object to act as a a buffer to store the results of a bunch of threads that can also be accessed by the UI. You still need to think about thread safety but because only one copy of the object can exist inside your application all of the threads can use it to share information. You could also use it as a old fashioned “Global Variable” from your VB6 days, but personally I think that using it for that is bad software design. The main thing that makes something a singleton is making it’s constructor private. How do you create an object with a private constructor? Well check out this code:

  Public Class GlobalSettings

    Private Shared mySelf As GlobalSettings

    Private Sub New()

    End Sub

    Public Shared ReadOnly Property GetInstance() As GlobalSettings

      Get

        If mySelf Is Nothing Then

          mySelf = New GlobalSettings

        End If

        Return mySelf

      End Get

    End Property

  End Class

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