VBA類繼承

我正在撰寫一個腳本來幫助我根據用戶輸入在 3D 軟體中創建幾何圖形，我想用類來解決這個問題。我有 3 級結構、點、曲線和曲面，所以我想為每個創建一個類，其中下一級結構繼承較低的結構。因此，例如類 cPoint 有 4 個屬性：x、y、z、id。此外，cCurve 類只有 2 個屬性：id 和 points，表面也是如此。現在我的問題是：我實作了類 cPoint 如下：

Private x_ As Double
Private y_ As Double
Private z_ As Double
Private id_ As Long

Public Property Let X(ByVal value As Double)
    x_ = value
End Property
Public Property Let Y(ByVal value As Double)
    y_ = value
End Property
Public Property Let Z(ByVal value As Double)
    z_ = value
End Property
Public Property Let ID(ByVal value As Long)
    id_ = value
End Property
Public Property Get X() As Double
    X = x_
End Property
Public Property Get Y() As Double
    Y = y_
End Property
Public Property Get Z() As Double
    Z = z_
End Property
Public Property Get ID() As Long
    ID = id_
End Property

這里一切都很好。在這里，我實作了類 cCurve：

Implements cPoint

Private id_ As Long
Private point_ As Collection

Public Property Let ID(ByVal value As Long)
    id_ = value
End Property
Public Property Set point(ByVal value As Collection)
    Set point_ = value
End Property
Public Property Get ID() As Long
    ID = id_
End Property
Public Property Get point() As Collection
    Set point = point_
End Property

但是在這里，當我嘗試運行代碼時，我收到以下錯誤提示： Object module needs to implement 'X' for interface 'cPoint' 我想我知道這意味著什么，但我不知道如何實作它。我的方法是否正確？我非常感謝以這種方式提供的任何指導。

uj5u.com熱心網友回復：

VBA 不支持繼承。模仿繼承的唯一方法是實作 Point 類，同時在曲線類中擁有 Point 類的私有實體。這就是您的“Point”類的樣子（我使用“GeometryPoint”作為類的名稱，因為 Excel 已經創建了一個“Point”類）：

Option Explicit

Private Type TState
    ID  As Long
    X   As Double
    Y   As Double
    Z   As Double
End Type

Private This As TState

Public Property Let ID(ByVal Value As Long)
    This.ID = Value
End Property
Public Property Get ID() As Long
    ID = This.ID
End Property

Public Property Let X(ByVal Value As Double)
    This.X = Value
End Property
Public Property Get X() As Double
    X = This.X
End Property

Public Property Let Y(ByVal Value As Double)
    This.Y = Value
End Property
Public Property Get Y() As Double
    Y = This.Y
End Property

Public Property Let Z(ByVal Value As Double)
    This.Z = Value
End Property
Public Property Get Z() As Double
    Z = This.Z
End Property

這就是你的“曲線”類的樣子：

Option Explicit
Implements GeometryPoint

Private Type TState
    Base        As GeometryPoint
    ID          As Long
    Points      As Collection
    X           As Double
    Y           As Double
    Z           As Double
End Type

Private This As TState

Public Property Let GeometryPoint_ID(ByVal Value As Long)
    This.Base.ID = Value
End Property
Public Property Get GeometryPoint_ID() As Long
    GeometryPoint_ID = This.Base.ID
End Property

Public Property Let GeometryPoint_X(ByVal Value As Double)
    This.Base.X = Value
End Property
Public Property Get GeometryPoint_X() As Double
    GeometryPoint_X = This.Base.X
End Property

Public Property Let GeometryPoint_Y(ByVal Value As Double)
    This.Base.Y = Value
End Property
Public Property Get GeometryPoint_Y() As Double
    GeometryPoint_Y = This.Base.Y
End Property

Public Property Let GeometryPoint_Z(ByVal Value As Double)
    This.Base.Z = Value
End Property
Public Property Get GeometryPoint_Z() As Double
    GeometryPoint_Z = This.Base.Z
End Property

Public Property Set Points(ByVal Value As Collection)
    Set This.Points = Value
End Property
Public Property Get Points() As Collection
    Set Points = This.Points
End Property

Private Sub Class_Initialize()
    Set This.Base = New GeometryPoint
End Sub

Private Sub Class_Terminate()
    Set This.Base = Nothing
End Sub

In VBA, when you "Implement" a class you need to list all of the members (properties, methods) of that class. In your case you received an error because you didn't list the X,Y,Z properties of the cPoint class that you were implementing. Is the "Curve" class supposed to have X,Y,Z properties as well? If not then you shouldn't implement the Point class. If the Curve class is just a class that stores a collection of Points then your Curve class should look like this:

**Note: This code was edited to include the "Class_Initialize" method which sets the "Points" member as a new collection once the Curve class is instantiated.

Option Explicit

Private Type TState
    ID          As Long
    Points      As Collection
End Type

Private This As TState

Public Property Let ID(ByVal Value As Long)
    This.ID = Value
End Property
Public Property Get ID() As Long
    ID = This.ID
End Property

Public Property Set Points(ByVal Value As Collection)
    Set This.Points = Value
End Property
Public Property Get Points() As Collection
    Set Points = This.Points
End Property

Private Sub Class_Initialize()
    Set This.Points = New Collection
End Sub

Private Sub Class_Terminate()
    Set This.Points = Nothing
End Sub

Finally, adding a new Point object to the "Points" member in the Curve class would look something like this:

Dim NewPoint As GeometryPoint
Dim NewCurve As Curve

Set NewPoint = New GeometryPoint
With NewPoint
    .X = 1
    .Y = 2
    .Z = 3
End With

Set NewCurve = New Curve
With NewCurve.Points
    .Add NewPoint
End With

標籤：vba 班级 遗产

上一篇：介面擴展是否等同于繼承？（爪哇）

下一篇：在mongodb中哪種方式更合理？