vba （错误 91：未设置对象变量或块变量）在 Visual Basic 6.0 中声明和访问全局变量时出错
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(Error 91 : object variable or with block variable not set) Error in declaring and accessing global variable in Visual Basic 6.0
提问by Pragya Dalal
I am designing a login form. I have done global declaration in in a module:
我正在设计一个登录表单。我在一个模块中做了全局声明：
Global db As ADODB.Connection
Global rs As ADODB.Recordset
Global tot As Integer
Public Sub access_connector()
Set db = New ADODB.Connection
db.Provider = "Microsoft.jet.oledb.4.0"
db.CursorLocation = adUseClient
db.Open App.Path & "\data.mdb"
End Sub
And in the form's code window :
在表单的代码窗口中：
Private Sub Command1_Click()
db.Open
Set rs = db.Execute("SELECT * FROM Login Where UserName='" _
& txtusername.Text & "'")
If txtpassword = "" And txtusername = "" Then
MsgBox "Login not possible"
Else
If Not rs.EOF() Then
If (rs(1) = txtpassword.Text) Then
MsgBox "Login Successful"
Else
MsgBox "Login not success"
End If
Else
MsgBox "EOF Reached"
End If
End If
db.Close
End Sub
But when I click on Login button the following error occurs : Error 91 : object variable or with block variable not set
但是，当我单击登录按钮时，会发生以下错误： 错误 91：未设置对象变量或块变量
Actually I think (may not be true) it is not able to recognize "db" and "rs" objects, as while debugging "db.open" is highlighted.
实际上我认为（可能不是真的）它无法识别“db”和“rs”对象，因为在调试“db.open”时突出显示。
Can anyone please solve this problem. I would be very thankful. Thanks in advance.
任何人都可以解决这个问题。我会很感激的。提前致谢。
回答by Doug Glancy
I changed the name of your "db" variable to "conn" to emphasize the fact that it's a connection, not a database. Then, you should open the connection when you need it, in the form. You have to specify the database in the form, as you haven't declared a database variable earlier. Probably you should re-think the global ADODB variables and just include them in your form code, but I'm not sure about that.
我将“db”变量的名称更改为“conn”以强调它是一个连接而不是数据库的事实。然后，您应该在需要时以表单打开连接。您必须在表单中指定数据库，因为您之前没有声明数据库变量。可能您应该重新考虑全局 ADODB 变量并将它们包含在您的表单代码中，但我不确定这一点。
Global conn As ADODB.Connection
Global tot As Integer
Public Sub access_connector()
Set conn = New ADODB.Connection
conn.Provider = "Microsoft.jet.oledb.4.0"
conn.CursorLocation = adUseClient
End Sub
Private Sub Command1_Click()
Dim rs As ADODB.Recordset
access_connector
conn.Open App.Path & "\data.mdb"
Set rs = conn.Execute("SELECT * FROM Login Where UserName='" & txtusername.Text & "'")
If txtpassword = "" And txtusername = "" Then
MsgBox "Login not possible"
Else
If Not rs.EOF() Then
If (rs(1) = txtpassword.Text) Then
MsgBox "Login Successful"
Else
MsgBox "Login not success"
End If
Else
MsgBox "EOF Reached"
End If
End If
conn.Close
End Sub
