“对象变量或未设置块变量"VB6 中的运行时错误 [英] "Object variable or With block variable not set" runtime error in VB6

问题描述

我遇到了 VB6 的问题.我有一个表格，上面有几个 ComboBox 对象.我希望通过一个将 SQL 查询作为参数的函数来填充 ComboBoxes.所以代码是这样的

I've got a problem with VB6. I have a form with several ComboBox objects on it. I wish to populate the ComboBoxes via a function that takes a SQL query as a parameter. So the code looks like this

Private Function FillComboBoxFromMDB(ByVal sDBName As String, _
                                     ByVal sSQL As String) As ComboBox
    '/*
    ' * Execute SQL in MDB and fill the ComboBox with the results
    ' * Returns filled ComboBox
    ' */
    Dim DB As Database
    Dim DBRecordset As Recordset

    On Error GoTo FillComboBoxFromMDB_ErrHandler

    Set DB = OpenDatabase(sDBName, False, False)

    If Not DB Is Nothing Then
        Set DBRecordset = DB.OpenRecordset(sSQL)
        If Not DBRecordset Is Nothing Then
            If DBRecordset.RecordCount > 0 Then
                Call FillComboBoxFromMDB.AddItem(DBRecordset.Fields(0).Value)
                ' ^^ This row gives the "Object variable or With block variable not set"
            End If
        Else
            Call WriteLog("Unable to execute " & sSQL)
        End If
        DB.Close
    Else
        Call WriteLog("Unable to open " & sDBName)
    End If

    Exit Function
FillComboBoxFromMDB_ErrHandler:
    Call WriteLog("FillComboBoxFromMDB() error: " & Err.Number & " " & Err.Description)
End Function

我这样调用函数.

Private Function Test()
    ' Fill the combobox
    frmMyForm.cmbMyCombo = FillComboBoxFromMDB("Database.mdb", _
                                               "SELECT MyTable.MyText FROM MyTable")
End Function

所以基本上我明白这归结为实例化，但我没有在网上找到任何有用的东西.New 关键字不像在 VB.Net 中那样工作.如何实例化 FillComboBoxFromMDB 组合框以使该函数起作用?有没有可能?

So basically I understand that this comes down to instantiation, but I haven't found anything useful about it online. The New keyword doesn't work like it works in VB.Net. How do I instantiate the FillComboBoxFromMDB combobox so that the function will work? Is it even possible?

提前致谢！

推荐答案

你的代码表达了这样一种信念，即标识符 FillComboBoxFromMDB 已经获得了对赋值左侧的组合框的引用测试程序.

You code expresses the belief that the identifier FillComboBoxFromMDB has acquired a reference to the combobox on the left hand side of the assignment in the Test procedure.

如果函数尝试(但失败)将结果分配给左侧，则函数不会首先执行 FillCombBoxFromMDB 为 Nothing.

This is not the case the function will execute first with FillCombBoxFromMDB being Nothing once it it would attempt (and fail) to assign the result to the left hand side.

您需要将组合框作为参数传递.

You need to pass the combobox as a parameter.

Private Sub FillComboBoxFromMDB(ByVal sDBName As String, _
                                     ByVal sSQL As String, ByVal cbo As ComboBox)
    '/*
    ' * Execute SQL in MDB and fill the ComboBox with the results
    ' * Returns filled ComboBox
    ' */
    Dim DB As Database
    Dim DBRecordset As Recordset

    On Error GoTo FillComboBoxFromMDB_ErrHandler

    Set DB = OpenDatabase(sDBName, False, False)

    If Not DB Is Nothing Then
        Set DBRecordset = DB.OpenRecordset(sSQL)
        If Not DBRecordset Is Nothing Then
            If DBRecordset.RecordCount > 0 Then
                Call cbo.AddItem(DBRecordset.Fields(0).Value)
                ' ^^ This row gives the "Object variable or With block variable not set"
            End If
        Else
            Call WriteLog("Unable to execute " & sSQL)
        End If
        DB.Close
    Else
        Call WriteLog("Unable to open " & sDBName)
    End If

    Exit Sub
FillComboBoxFromMDB_ErrHandler:
    Call WriteLog("FillComboBoxFromMDB() error: " & Err.Number & " " & Err.Description)
End Sub

这样称呼它:-

 Private Function Test()
 ' Fill the combobox
 Call FillComboBoxFromMDB("Database.mdb", _
                          "SELECT MyTable.MyText FROM MyTable", _
                          frmMyForm.cmbMyCombo ) 
 End Function

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