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Singleton Object Pattern with generic sauce, mutex protection and chips

Sat, 05/24/2008 - 14:44 — geri

Ever got tired of rewriting the same 10-15 lines of Singleton Object implementation code for each class U use it? Met the flexibility of the inherited static member variables, sparks of the overridable static methods?

''' <summary>
''' Application global instance of T type object
''' </summary>
''' <typeparam name="T"></typeparam>
''' <remarks></remarks>
Public Class SingletonObject(Of T)

    ''' <summary>
    ''' The Object itself
    ''' </summary>
    ''' <remarks></remarks>
    Private Shared _instance As T

    ''' <summary>
    ''' This will come handy by the multi-threaded use 
    ''' </summary>
    ''' <remarks></remarks>
    Private Shared _lockObject As Object = New Object()

    ''' <summary>
    ''' The constructor is private, don't tinker with it
    ''' </summary>
    ''' <remarks></remarks>
    Private Sub New()
    End Sub

    ''' <summary>
    ''' The method examines if an object is already instaniated, if not
    ''' synclocks the empty object, and creates a new instance
    ''' </summary>
    ''' <returns>T</returns>
    ''' <remarks>Instead of TypeDescriptor you may use Activator, only a matter of taste</remarks>
    Public Shared Function GetObject() As T
        If IsNothing(_instance) Then
            SyncLock (_lockObject)
                If _instance Is Nothing Then _
                System.ComponentModel.TypeDescriptor.CreateInstance(Nothing, GetType(T), Nothing, Nothing)
            End SyncLock
        End If
        Return _instance
    End Function

End Class

The C# implementation will hopefully come soon by Maci

(ps: Don't try to dump any class into the code which has only parameterized constructor, it may cause an interresting exception by the instaniation...)