Question

在涉及虚拟函数的虚拟继承的情况下，有人可以解释一下类的大小吗？代码如下：

[Sub JSONPull()
Dim WB As Workbook, ws As Worksheet, ws2 As Worksheet, qtb As QueryTable
Dim FC As String, sDate As String, eDate As String, Dockmasterurl As String, Performance As Worksheet

Set WB = Application.ThisWorkbook
Set ws = WB.Sheets("Control")

FC = ws.Range("B5")
sDate = ws.Range("B14")
eDate = ws.Range("B15")
Dim sJSONString As String
    Dim vJSON
    Dim sState As String
    Dim aData()
    Dim aHeader()
    Dim vResult

Dockmasterurl = "https://fc-inbound-dock-execution-service-eu-eug1-dub.dub.proxy.amazon.com/appointment/bySearchParams?warehouseId=" & FC & "&clientId=dockmaster&localStartDate=" & sDate & "T00%3A00%3A00&localEndDate=" & eDate & "T08%3A00%3A00&isStartInRange=false&searchResultLevel=FULL"

Set ws2 = Sheets("JSON")
ws2.Cells.ClearContents

Set qtb = ws2.QueryTables.Add("URL;" & Dockmasterurl, ws2.Range("A1"))
With qtb
    .WebSelectionType = xlEntirePage
    .WebFormatting = xlWebFormattingNone
    .WebPreFormattedTextToColumns = True
    .WebConsecutiveDelimitersAsOne = True
    .WebSingleBlockTextImport = True
    .WebDisableDateRecognition = False
    .WebDisableRedirections = False
    .Refresh BackgroundQuery:=False
End With

ws2.Columns("A:A").TextToColumns Destination:=Range("A1"), DataType:=xlDelimited, textqualifier:=xlDoubleQuote, consecutivedelimiter:=False, comma:=True, trailingminusnumbers:=True
ws2.Range("A:S").EntireColumn.AutoFit

For Each qtb In ws2.QueryTables
    qtb.Delete

Next

End Sub][1]

B类的大小为48。

Answer 1

这取决于您的实现。在您的示例中，除了较差的实现之外，没有理由在64位计算机上选择sizeof（B）> 32。

在通常的实现中，“虚拟”类（一个具有虚拟方法或基类的类）需要为每个虚拟基数使用vtable指针（如果有虚拟方法而没有虚拟基数，则至少为一个），如果在某些情况下还有其他（非虚拟）基础，则可能需要其他vtable指针。还有一些优化措施可以减少这种情况（尤其是链接时类的布局）。

虚拟继承的情况下类的意外大小

1 个答案: