“对象变量或未设置块变量"表示“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
我对VB6有问题.我有一个带有几个ComboBox对象的表单.我希望通过将SQL查询作为参数的函数来填充ComboBoxes.所以代码看起来像这样
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
因此，基本上，我知道这归结于实例化，但是我没有在网上找到任何有用的东西. New关键字无法像在VB.Net中那样起作用.如何实例化FillComboBoxFromMDB组合框，以便该功能正常工作?甚至有可能吗?
提前谢谢！
您的代码表达了一种信念，即标识符FillComboBoxFromMDB已获得对测试"过程中分配左侧的组合框的引用.
不是这种情况，一旦它将尝试(失败)将结果分配给左侧时，该函数将首先在FillCombBoxFromMDB为Nothing的情况下执行.
您需要将组合框作为参数传递.
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
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
I call the function like this.
Private Function Test()
' Fill the combobox
frmMyForm.cmbMyCombo = FillComboBoxFromMDB("Database.mdb", _
"SELECT MyTable.MyText FROM MyTable")
End Function
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?
Thanks in advance!
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.
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.
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
Call it like this:-
Private Function Test()
' Fill the combobox
Call FillComboBoxFromMDB("Database.mdb", _
"SELECT MyTable.MyText FROM MyTable", _
frmMyForm.cmbMyCombo )
End Function
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