vb中的单例模式 [英] singleton pattern in vb

问题描述

我通常是一名 c# 程序员，但现在我在 VB 中为这个项目工作，当我用来设置一个单例类时，我会遵循 Jon Skeet 模型

I am normally a c# programmer but am now working in VB for this one project when I use to set up a singleton class I would follow the Jon Skeet model

public sealed class Singleton
{
    static Singleton instance = null;
    static readonly object padlock = new object();

    Singleton()
    {
    }

    public static Singleton Instance
    {
        get
        {
            lock (padlock)
            {
                if (instance == null)
                {
                    instance = new Singleton();
                }
                return instance;
            }
        }
    }

    //Added to illustrate the point
    public static void a()
    {
    }

    public void b()
    {
    }

} 

或者现在的变体之一，如果我用 c# 编写语句

or one of the variations now if I write the statement in c#

Singleton.Instance 什么是所有非静态成员，b而不是a.

Singleton.Instance What procedures is all of the members that are not static, b but not a.

现在当我在 VB 中做同样的事情时

Now when I do the same in VB

Private Shared _instance As StackTracker
Private Shared ReadOnly _lock As Object = New Object()
Private Sub New()
    _WorkingStack = New Stack(Of MethodObject)
    _HistoryStack = New Queue(Of MethodObject)
End Sub

Public Shared ReadOnly Property Instance() As StackTracker
    Get
        SyncLock _lock
            If (_instance Is Nothing) Then
                _instance = New StackTracker()
            End If
        End SyncLock

        Return _instance
    End Get

End Property

我得到了 StackTracker.Instance.Instance 并且它继续运行，虽然它看起来很糟糕，但并不是世界末日.

I get StackTracker.Instance.Instance and it keeps going, while it is not the end of the world it looks bad.

问题在VB中有没有办法隐藏第二个实例，这样用户就不能递归调用实例?

Question is there a way in VB to hide the second instance so the user can not recursively call Instance?

推荐答案

完整代码如下:

Public NotInheritable Class MySingleton
    Private Shared ReadOnly _instance As New Lazy(Of MySingleton)(Function() New
        MySingleton(), System.Threading.LazyThreadSafetyMode.ExecutionAndPublication)

    Private Sub New()
    End Sub

    Public Shared ReadOnly Property Instance() As MySingleton
        Get
            Return _instance.Value
        End Get
    End Property
End Class

然后使用这个类，获取实例使用:

Then to use this class, get the instance using:

Dim theSingleton As MySingleton = MySingleton.Instance

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