按F5运行程序;在弹出的属性对话框中,选中"Wait for Components to
Start"(启动工程时等待创建部件),然后按[OK]按钮;
这时,类就会被激活,其他程序就可使用它的功能。
再次运行Visual
Basic另一个实例;
创建一个新的"Standard
EXE"工程;
选择"'Project"->"References"菜单;
浏览对话框中可引用的列表项,可以发现一些额外的组件。
选中"Northwind"列表项;
Northwind就是前面创建的ActiveX工程。
单击[OK]按钮;
现在添加一些代码来使用上述工程:
在Form1表单中添加一个命令按钮;为命令按钮添加下列代码:
Dim Test As Customers Set Test = New Customers MsgBox
Test.CustomerID Set Test =
Nothing 该代码首先创建一个新的Customers对象,然后显示CustomerID信息,最后将Test对象置为Nothing,并关闭它。
Dim Test As Customers Set Test = New
Customers Test.CustomerID = "KARLY" Test.Update MsgBox
Test.CustomerID Set Test =
Nothing 该代码首先设置"CustomerID"字段,然后更新记录集,最后显示出CustomerID属性,其结果应该是设置的"KARLY"。
Dim WithEvents rs As Recordset Public Event
RecordsetMove() Private Sub Class_Initialize() Set rs = New
Recordset rs.ActiveConnection = "Provider=Microsoft." &
_"Jet.OLEDB.4.0;Data Source=C:\Program Files\" & _"Microsoft Visual
Studio\VB98\Nwind.mdb;" & _"Persist Security Info=False" rs.Open
"select * from customers", , adOpenKeyset, adLockOptimistic End
Sub
Private Sub Class_Terminate() rs.Close Set rs =
Nothing End Sub
Public Property Get CustomerID() As
String CustomerID = rs("CustomerID") End
Property
Public Property Let CustomerID(NewValue As
String) 'If the length of NewValue is greater than five If
Len(NewValue) > 5 Then '... then raise an error to the
program 'using this class, by running 'Err.Raise
vbObjectError + OurErrorNumber Err.Raise vbObjectError + 1,
"CustomerID", _"Customer ID can only be up to five " & _ "characters
long!"
Else '... otherwise, change the field
value rs("CustomerID") = NewValue End If End
Property Public Property Get CompanyName() As
Variant CompanyName = rs("CompanyName") End
Property
Public Property Let CompanyName(ByVal NewValue As
Variant) rs("CompanyName") = NewValue End
Property
Public Property Get ContactName() As
Variant ContactName = rs("ContactName") End
Property
Public Property Let ContactName(ByVal NewValue As
Variant) rs("ContactName") = NewValue End
Property
Public Property Get ContactTitle() As
Variant ContactTitle = rs("ContactTitle") End
Property
Public Property Let ContactTitle(ByVal NewValue As
Variant) rs("ContactTitle") = NewValue End
Property
Public Property Get Address() As Variant Address =
rs("Address") End Property
Public Property Let Address(ByVal
NewValue As Variant) rs("Address") = NewValue End
Property
Public Property Get City() As Variant City =
rs("City") End Property
Public Property Let City(ByVal
NewValue As Variant) rs("City") = NewValue End
Property
Public Property Get Region() As Variant Region =
rs("Region") End Property
Public Property Let Region(ByVal
NewValue As Variant) rs("Region") = NewValue End
Property
Public Property Get PostalCode() As
Variant PostalCode = rs("PostalCode") End
Property
Public Property Let PostalCode(ByVal NewValue As
Variant) rs("PostalCode") = NewValue End
Property
Public Property Get Country() As Variant Country =
rs("Country") End Property
Public Property Let Country(ByVal
NewValue As Variant) rs("Country") = NewValue End
Property
Public Property Get Phone() As Variant Phone =
rs("Phone") End Property
Public Property Let Phone(ByVal
NewValue As Variant) rs("Phone") = NewValue End
Property
Public Property Get Fax() As Variant Fax =
rs("Fax") End Property
Public Property Let Fax(ByVal
NewValue As Variant) rs("Fax") = NewValue End
Property
Public Sub AddNew() rs.AddNew End
Sub
Public Sub Update() rs.Update End
Sub
Public Sub CancelUpdate() If rs.EditMode =
adEditInProgress Or _rs.EditMode = adEditAdd
Then rs.CancelUpdate End If End Sub Public Sub
MoveNext() rs.MoveNext End Sub
Public Sub
MovePrevious() rs.MovePrevious End Sub
Public Sub
MoveFirst() rs.MoveFirst End Sub
Public Sub
MoveLast() rs.MoveLast End Sub
Public Function
FindByCustomerID(CustomerID As String) As Boolean 'Uses the Find
method to locate customers 'with a matching
CustomerID. 'Returns True value is customer(s) found Dim
varBookmark As Variant rs.MoveFirst rs.Find ("CustomerID='"
& CustomerID & "'") If rs.EOF = True
Then FindByCustomerID = False rs.Bookmark =
varBookmark Else FindByCustomerID = True End
If End Function
Public Property Get EOF() As
Boolean 'Example of a read-only property No Property Lets
here EOF = rs.EOF End Property Public Property Get BOF() As
Boolean 'Another example of a read-only property BOF =
rs.BOF End Property Private Sub rs_MoveComplete(ByVal adReason
As ADODB.EventReasonEnum, _ ByVal pError As ADODB.Error,
adStatus As ADODB.EventStatusEnum, _ ByVal pRecordset As
ADODB.Recordset)
'Reacts to the recordset
MoveComplete 'method - raises event with each move RaiseEvent
RecordsetMove End
Sub 需要说明的是:迄今为止,我们仅仅是在一个类中添加代码。当然,也可以选择"Project"->"Add
Class"菜单来向工程添加多个类,而且还可利用"collections"使这些类工作在一起。但是在这里,我们仍然想用一个类来处理一个数据表。