Extend Collections Class VBA

Question

我已经创建了一个排序函数来允许基于其中一个对象属性对自定义对象的实例进行排序。是否可以扩展VBA中的现有集合类？我不相信VBA支持继承，所以我不知道如何以适当的方式去解决这个问题。我可以创建一个新模块并将该函数放置在该模块中，但这似乎不是实现该模块的最佳方式。

Answer 1

感谢您的回复。我最终创建了自己的类，它扩展了VBA中的Collections类。如果任何人有兴趣，以下是代码。

'Custom collections class is based on the Collections class, this class extendes that 
'functionallity so that the sort method for a collection of objects is part of 
'the class. 

'One note on this class is that in order to make this work in VBA, the Attribute method has to be added 
'manually. To do this, create the class, then export it out of the project. Open in a text editor and 
'add this line Attribute Item.VB_UserMemId = 0 under the Item() function and this line 
'Attribute NewEnum.VB_UserMemId = -4 under the NewEnum() function. Save and import back into project. 
'This allows the Procedure Attribute to be recognized. 

Option Explicit 

Private pCollection As Collection 

Private Sub Class_Initialize() 
    Set pCollection = New Collection 
End Sub 

Private Sub Class_Terminate() 
    Set pCollection = Nothing 
End Sub 

Function NewEnum() As IUnknown 
    Set NewEnum = pCollection.[_NewEnum] 
End Function 

Public Function Count() As Long 
    Count = pCollection.Count 
End Function 

Public Function item(key As Variant) As clsCustomCollection 
    item = pCollection(key) 
End Function 

'Implements a selection sort algorithm, could likely be improved, but meets the current need. 
Public Sub SortByProperty(sortPropertyName As String, sortAscending As Boolean) 

    Dim item As Object 
    Dim i As Long 
    Dim j As Long 
    Dim minIndex As Long 
    Dim minValue As Variant 
    Dim testValue As Variant 
    Dim swapValues As Boolean 

    Dim sKey As String 

    For i = 1 To pCollection.Count - 1 
     Set item = pCollection(i) 
     minValue = CallByName(item, sortPropertyName, VbGet) 
     minIndex = i 

     For j = i + 1 To pCollection.Count 
      Set item = pCollection(j) 
      testValue = CallByName(item, sortPropertyName, VbGet) 

      If (sortAscending) Then 
       swapValues = (testValue < minValue) 
      Else 
       swapValues = (testValue > minValue) 
      End If 

      If (swapValues) Then 
       minValue = testValue 
       minIndex = j 
      End If 

      Set item = Nothing 
     Next j 

     If (minIndex <> i) Then 
      Set item = pCollection(minIndex) 

      pCollection.Remove minIndex 
      pCollection.Add item, , i 

      Set item = Nothing 
     End If 

     Set item = Nothing 
    Next i 

End Sub 

Public Sub Add(value As Variant, key As Variant) 
    pCollection.Add value, key 
End Sub 

Public Sub Remove(key As Variant) 
    pCollection.Remove key 
End Sub 

Public Sub Clear() 
    Set m_PrivateCollection = New Collection 
End Sub 

Answer 2

我会创建一个包装类，公开对象的属性，用你自己的替换sort函数。

Answer 3

一种流行的选择是使用一个ADO disconnected recordset作为一种hyperpowered收集/字典对象，它有内置的支持Sort的。虽然您正在使用ADO，但您仍可使用don't need a database。