Question

我想知道是否存在等价的（.net）

list<somefixedclass>

in vb6

我知道vb6中存在集合，但它使用对象（变体）而不是特定对象。

感谢。

Answer 1

VB 6中没有与VB.NET中的通用List<T>直接等价的东西。但是，VB 6中存在Collection这样的东西，它提供了类似的功能。主要区别在于VB 6 Collection 不是强类型，这意味着所有对象都存储为集合中的Variants。在某些情况下，这可能是有益的，因为它允许您在同一个集合中存储许多不同类型的数据，事实上，VB在内部使用此对象。从类中检索它们时，使用Collection和上传对象很容易，但是你几乎无能为力。在VB运行时中无法实现强类型集合。

话虽如此，您可以实施一种解决方法。类似于在引入泛型之前如何在早期版本的VB.NET中实现集合，您可以将Collection包装在一个类中，其中对内部Collection的唯一访问是通过以下方法你从这个类中公开。此设计模式通常称为“自定义集合”。

这确实有自动处理强制转换的好处，并减轻代码的使用者必须记住这样的实现细节。它会处理（很可能）您在运行时循环遍历集合的可能性，该集合只应包含一种类型的对象，但意外地添加了第二种不兼容的对象类型，导致您的代码抛出异常。当然，缺点是您必须以自定义集合上的公共方法的形式重新实现Collection对象本身提供的大部分功能。

以下是您可以采用的示例：

Public Class CustomerCollection

    ''#Internal collection, exposed by this class
    Private m_Customers As Collection

    Private Sub Class_Initialize()
        ''#Set up the internal collection
        Set m_Customers = New Collection
    End Sub

    Public Sub Add(ByVal cust as Customer, Optional ByVal key as String)
        ''#Add the Customer object to the internal collection
        If IsMissing(key) Then
            m_Customers.Add cust
        Else
            m_Customers.Add cust, key
        End If
    End Sub

    Public Property Get Count() As Integer
        ''#Return the number of objects in the internal collection
        Count = m_Customers.Count
    End Property

    Public Sub Remove(ByVal index As Variant)
        ''#Remove the specified object from the internal collection,
        ''# either by its index or its key
        m_Customers.Remove index
    End Sub

    Public Function Item(ByVal index As Variant) as Customer
        ''#Return the specified object from the internal collection,
        ''# either by its index or its key
        Set Item = m_Customers.Item(index)
    End Function

    Public Sub Clear()
        ''#Removes all objects from the internal collection
        Set m_Customers = New Collection
    End Sub

End Class

请注意，为了将自定义集合的Item属性设置为集合的默认方法（如内置Collection对象），您需要在VB 6 IDE中执行以下步骤：< / p>

从“工具”菜单中，单击“过程属性”
从“名称”组合框中选择自定义类的名称。
出现对话框时，单击“高级”按钮。
在“过程ID”组合框中选择“（默认）”项。
点击“确定”

如果您还希望使用For Each语法（也类似于内置的Collection对象）允许枚举自定义类，则可以向自定义类添加NewEnum函数：

Public Property Get NewEnum() As IUnknown
    ''#Provides support for enumeration using For Each
    Set NewEnum = m_Customers.[_NewEnum]
End Property

完成后，您需要指示VB使用此属性：

和以前一样，从“工具”菜单中打开“过程属性”对话框
从“名称”组合框中选择自定义类的名称。
出现对话框时，单击“高级”按钮。
在“程序ID”组合框中输入数字“-4”。
点击“确定”

Answer 2

这是我们对ArrayList的实现。对于强类型类，您可以将它用作基础（不是通过显然继承，而是通过CodyGray的答案中表达的组合），但如果您不需要类型安全，则它比Collection类好得多。

Option Explicit

Private mavInternalArray() As Variant
Private mlArraySize As Long
Private mlCount As Long
Private mlGrowSize As Long
Private mfZeroIndex As Boolean

'---------------------------------------------------------------------------------------
' Procedure Clear
'---------------------------------------------------------------------------------------
Public Sub Clear()
          Dim index As Long

        For index = 0 To mlCount - 1
            If IsObject(mavInternalArray(index)) Then
                Set mavInternalArray(index) = Nothing
            End If
        Next index
        mlCount = 0

End Sub



'---------------------------------------------------------------------------------------
' Procedure Swap
'---------------------------------------------------------------------------------------
Public Sub Swap(Index1 As Long, index2 As Long)
          Dim vTmp As Variant


        If IsObject(mavInternalArray(index2)) Then
            Set vTmp = mavInternalArray(index2)
        Else
            vTmp = mavInternalArray(index2)
        End If

        If IsObject(mavInternalArray(Index1)) Then
            Set mavInternalArray(index2) = mavInternalArray(Index1)
        Else
           mavInternalArray(index2) = mavInternalArray(Index1)
       End If

       If IsObject(vTmp) Then
           Set mavInternalArray(Index1) = vTmp
       Else
           mavInternalArray(Index1) = vTmp
       End If


End Sub

Public Property Get ZeroIndex() As Boolean
        ZeroIndex = mfZeroIndex
End Property

Public Property Let ZeroIndex(fZeroIndex As Boolean)
        mfZeroIndex = fZeroIndex
End Property

Public Property Get GrowSize() As Long
        GrowSize = mlGrowSize
End Property

Public Property Let GrowSize(lNewSize As Long)
        Debug.Assert lNewSize > 0
        mlGrowSize = lNewSize
End Property

Private Sub Class_Initialize()
        mlGrowSize = 50
        mlArraySize = mlGrowSize
        mfZeroIndex = True
        mlCount = 0


        ReDim mavInternalArray(0 To mlGrowSize - 1)

End Sub

'---------------------------------------------------------------------------------------
' Procedure Remove
'---------------------------------------------------------------------------------------
Public Sub Remove(index As Long)
        Dim index2 As Long


        For index2 = index To mlCount - 2
            If IsObject(mavInternalArray(index2 + 1)) Then
                Set mavInternalArray(index2) = mavInternalArray(index2 + 1)
            Else
                mavInternalArray(index2) = mavInternalArray(index2 + 1)
            End If
        Next index2
          If mlCount <= 0 Then
            Exit Sub
          End If
        mlCount = mlCount - 1
        If IsObject(mavInternalArray(mlCount)) Then
           Set mavInternalArray(mlCount) = Nothing
       Else
           mavInternalArray(mlCount) = False
       End If
End Sub

'---------------------------------------------------------------------------------------
' Procedure Items
'---------------------------------------------------------------------------------------
Public Function Items(index As Long) As Variant
        If Not mfZeroIndex Then
            index = index - 1
        End If

        If index < mlCount And index >= 0 Then
            If IsObject(mavInternalArray(index)) Then
                Set Items = mavInternalArray(index)
            Else
                Items = mavInternalArray(index)
            End If
       End If
End Function

Public Sub SetItem(index As Long, Item As Variant)
        If Not mfZeroIndex Then
            index = index - 1
        End If
        If IsObject(Item) Then
            Set mavInternalArray(index) = Item
        Else
            mavInternalArray(index) = Item
        End If
End Sub

'---------------------------------------------------------------------------------------
' Procedure Add
'---------------------------------------------------------------------------------------
Public Function Add(vItem As Variant) As Long

        mlCount = mlCount + 1
        If mlCount > mlArraySize Then
            mlArraySize = mlArraySize + mlGrowSize
            ReDim Preserve mavInternalArray(0 To mlArraySize - 1)
        End If

        If IsObject(vItem) Then
            Set mavInternalArray(mlCount - 1) = vItem
        Else
            mavInternalArray(mlCount - 1) = vItem
       End If

       Add = mlCount - 1

End Function

'---------------------------------------------------------------------------------------
' Procedure ItemArray
'---------------------------------------------------------------------------------------
Public Function ItemArray() As Variant
        Dim vReturnArray As Variant

        vReturnArray = mavInternalArray
        ReDim Preserve vReturnArray(0 To mlCount - 1)
        ItemArray = vReturnArray
End Function

Public Function Count() As Long
        Count = mlCount
End Function


'---------------------------------------------------------------------------------------
' Procedure Insert
'---------------------------------------------------------------------------------------
Public Function Insert(index As Long, vItem As Variant) As Long
        Dim index2 As Long

        'Make sure array is large enough for a new item
        mlCount = mlCount + 1
        If mlCount > mlArraySize Then
            mlArraySize = mlArraySize + mlGrowSize
            ReDim Preserve mavInternalArray(0 To mlArraySize - 1)
        End If

        'Bump all the items with a higher index up one spot

        If index >= mlCount - 1 Then
            If IsObject(vItem) Then
                Set mavInternalArray(mlCount - 1) = vItem
            Else
               mavInternalArray(mlCount - 1) = vItem
           End If
       Else

           For index2 = mlCount - 1 To index + 1 Step -1
               If IsObject(vItem) Then
                   Set mavInternalArray(index2) = mavInternalArray(index2 - 1)
               Else
                   mavInternalArray(index2) = mavInternalArray(index2 - 1)
               End If
           Next index2

           If IsObject(vItem) Then
               Set mavInternalArray(index) = vItem
           Else
               mavInternalArray(index) = vItem
           End If
       End If
       Insert = mlCount - 1

End Function


Public Sub Clone(ByRef cDestinationDynamicArray As clsDynamicArray)
        Dim index As Long

        If cDestinationDynamicArray Is Nothing Then
            Set cDestinationDynamicArray = New clsDynamicArray
        End If

        cDestinationDynamicArray.Clear

        For index = 0 To mlCount - 1
            Call cDestinationDynamicArray.Add(mavInternalArray(index))
        Next index

End Sub

Public Property Get NewEnum() As IUnknown
    ''#Provides support for enumeration using For Each
    Set NewEnum = m_Customers.[_NewEnum]
End Property

Answer 3

编辑：如果Cody Gray的解决方案太大而无法满足您的需求，您可以尝试使用“穷人列表”解决方案，如下所示：

 Dim l() as somefixedclass
 Redim l(0)

 '...
 'increase size dynamically:
 Redim Preserve l(ubound(l)+1)
 '...

当然，VB.NET中的List<somefixedclass>（在C＃中）或List(Of somefixedclass)更加“用户友好”，因为它有Find，Remove，AddRange和其他一些有用的东西。。旧的VB6构造与“空列表”案件的处理非常糟糕。不要忘记，List＆lt; ..＆gt;对于大型列表（大小> 1000），增加具有更好的性能。

Answer 4

VB6是一种古老的语言。它不包含类似于模板的类型，就像现代语言（C ++，C＃，Java）一样。因此，您必须将对象存储为集合中的变体，然后将它们转换回您的对象类型。

Answer 5

词典是包含任何对象的最佳方法。

vb6相当于list <someclass> </someclass>

5 个答案: