错误属性变量或返回属性时未设置块变量

问题描述

我正在尝试在VB6应用程序中使用我的COM类。我做了一些包装纸。当我创建对象时，我看到消息Is nothing 1，因此它表明已设置成员变量并且它不为null，但是当我尝试使用属性返回该成员时，则在返回行中看到异常Object variable or with block variable not set。我不知道如何解决它。

// MyComClass
This is a COM class with method Operation

// clsMyCom.cls
Private WithEvents m_myComClass As MyComClass

Private Sub Class_Initialize()
        
    If m_myComClass Is nothing Then
        MsgBox "Is nothing 1"
    End If
    
    Set m_myComClass = New MyComClass
    
    If m_myComClass Is nothing Then
        MsgBox "Is nothing 2"
    End If

End Sub

Public Property Get MyImplementation() As MyComClass

    If m_myComClass Is nothing Then
        MsgBox "Is nothing 3"
    End If
    
    // in this line I see exception:
    // object variable or with block variable not set
    MyImplementation = m_myComClass

End  Property

// usage
Dim variable As clsMyCom
Set variable = New clsMyCom
Call variable.MyImplementation.Operation(...)

解决方法

将方法更改为此：

Public Property Get MyImplementation() As MyComClass

    If m_myComClass Is Nothing Then
        MsgBox "Is Nothing 3"
    End If
    
    // in this line I see exception:
    // object variable or with block variable not set
    Set MyImplementation = m_myComClass

End  Property

为清楚起见，您错过了Set