VBA Excel错误处理 - 特别是在函数中 - 专业的Excel开发风格

Question

我得到了Rob Bovey的“专业Excel开发”一书，它让我大开眼界。

我正在使用错误处理重新编写代码。但是，有很多我不明白。我特别需要知道如何在函数中正确使用它。我使用Bovey的错误处理程序的重新抛出版本（在底部）。当我开始时，我使用基本的布尔（非重新抛出）方法并将我的子例程转换为布尔函数。 （P.S.我将基于答案切换回布尔方法。）

我需要有关如何将功能纳入此方案的指导。我希望它们返回它们的实际值（例如，如果在某些情况下它们失败，则为-1或-1），这样我就可以将它们嵌套在其他函数中，而不仅仅返回错误处理布尔值。

这是对bDrawCellBorders（myWS）的典型子例程调用在入口点内的样子。子呼叫似乎运行良好。 （即，它是一个仅被转换为函数的子例程，因此它可以向错误处理方案返回一个布尔值。）

Sub UpdateMe()  ' Entry Point

    Const sSOURCE As String = "UpdateMe()"

    On Error GoTo ErrorHandler

    Set myWS = ActiveCell.Worksheet
    Set myRange = ActiveCell
    myWS.Unprotect

' lots of code

    If Not bDrawCellBorders(myWS) Then ERR.Raise glHANDLED_ERROR    ' Call subroutine

' lots of code

ErrorExit:
    On Error Resume Next
    Application.EnableEvents = True
    myWS.Protect AllowFormattingColumns:=True
    Exit Sub

ErrorHandler:
    If bCentralErrorHandler(msMODULE, sSOURCE,,True) Then  ' Call as Entry Point
        Stop
        Resume
    Else
        Resume ErrorExit
    End If
End Sub

但是，我不知道如何将其扩展到实际功能。这是基于为子程序编写的书中的一个例子，我只是将其切换为一个函数。 问题：  *我怎么称呼它？它就像x = sngDoSomeMath（17）  *它的错误处理功能是否正常？  *使用bReThrow = true调用错误处理例程的正确位置在哪里？

Public Function sngDoSomeMath(ByVal iNum As Integer) As Single

Dim sngResult As Single

Const sSOURCE As String = "sngDoSomeMath()"

On Error GoTo ErrorHandler

' example 1, input did not pass validation. don't want to 
' go up the error stack but just inform the
' calling program that they didn't get a good result from this 
' function call so they can do something else
If iNum <> 42 Then
    sngResult = -1    'function failed because I only like the number 42
    GoTo ExitHere
End If

' example 2, true error generated
sngResult = iNum / 0

sngDoSomeMath = lResult

ExitHere:
    Exit Function
ErrorHandler:

' Run cleanup code
'  ... here if any

' Then do error handling

If bCentralErrorHandler(msMODULE, sSOURCE, , , True) Then ' The true is for RETHROW
    Stop
    Resume
End If

End Function

错误处理程序例程：

'
' Description:  This module contains the central error
'               handler and related constant declarations.
'
' Authors:      Rob Bovey, www.appspro.com
'               Stephen Bullen, www.oaltd.co.uk
'
' Chapter Change Overview
' Ch#   Comment
' --------------------------------------------------------------
' 15    Initial version
'
Option Explicit
Option Private Module

' **************************************************************
' Global Constant Declarations Follow
' **************************************************************
Public Const gbDEBUG_MODE As Boolean = False    ' True enables debug mode, False disables it.
Public Const glHANDLED_ERROR As Long = 9999     ' Run-time error number for our custom errors.
Public Const glUSER_CANCEL As Long = 18         ' The error number generated when the user cancels program execution.


' **************************************************************
' Module Constant Declarations Follow
' **************************************************************
Private Const msSILENT_ERROR As String = "UserCancel"   ' Used by the central error handler to bail out silently on user cancel.
Private Const msFILE_ERROR_LOG As String = "Error.log"  ' The name of the file where error messages will be logged to.


''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Comments: This is the central error handling procedure for the
'           program. It logs and displays any run-time errors
'           that occur during program execution.
'
' Arguments:    sModule         The module in which the error occured.
'               sProc           The procedure in which the error occured.
'               sFile           (Optional) For multiple-workbook
'                               projects this is the name of the
'                               workbook in which the error occured.
'               bEntryPoint     (Optional) True if this call is
'                               being made from an entry point
'                               procedure. If so, an error message
'                               will be displayed to the user.
'
' Returns:      Boolean         True if the program is in debug
'                               mode, False if it is not.
'
' Date          Developer       Chap    Action
' --------------------------------------------------------------
' 03/30/08      Rob Bovey       Ch15    Initial version
'
Public Function bCentralErrorHandler( _
       ByVal sModule As String, _
       ByVal sProc As String, _
       Optional ByVal sFile As String, _
       Optional ByVal bEntryPoint As Boolean, _
       Optional ByVal bReThrow As Boolean = True) As Boolean

    Static sErrMsg As String

    Dim iFile As Integer
    Dim lErrNum As Long
    Dim sFullSource As String
    Dim sPath As String
    Dim sLogText As String

    ' Grab the error info before it's cleared by
    ' On Error Resume Next below.
    lErrNum = ERR.Number
    ' If this is a user cancel, set the silent error flag
    ' message. This will cause the error to be ignored.
    If lErrNum = glUSER_CANCEL Then sErrMsg = msSILENT_ERROR
    ' If this is the originating error, the static error
    ' message variable will be empty. In that case, store
    ' the originating error message in the static variable.
    If Len(sErrMsg) = 0 Then sErrMsg = ERR.Description

    ' We cannot allow errors in the central error handler.
    On Error Resume Next

    ' Load the default filename if required.
    If Len(sFile) = 0 Then sFile = ThisWorkbook.Name

    ' Get the application directory.
    sPath = ThisWorkbook.Path
    If Right$(sPath, 1) <> "\" Then sPath = sPath & "\"

    ' Construct the fully-qualified error source name.
    sFullSource = "[" & sFile & "]" & sModule & "." & sProc

    ' Create the error text to be logged.
    sLogText = "  " & sFullSource & ", Error " & _
               CStr(lErrNum) & ": " & sErrMsg

    ' Open the log file, write out the error information and
    ' close the log file.
    iFile = FreeFile()
    Open sPath & msFILE_ERROR_LOG For Append As #iFile
    Print #iFile, Format$(Now(), "mm/dd/yy hh:mm:ss"); sLogText
    If bEntryPoint Or Not bReThrow Then Print #iFile,
    Close #iFile

    ' Do not display or debug silent errors.
    If sErrMsg <> msSILENT_ERROR Then

        ' Show the error message when we reach the entry point
        ' procedure or immediately if we are in debug mode.
        If bEntryPoint Or gbDEBUG_MODE Then
            Application.ScreenUpdating = True
            MsgBox sErrMsg, vbCritical, gsAPP_NAME
            ' Clear the static error message variable once
            ' we've reached the entry point so that we're ready
            ' to handle the next error.
            sErrMsg = vbNullString
        End If

        ' The return vale is the debug mode status.
        bCentralErrorHandler = gbDEBUG_MODE

    Else
        ' If this is a silent error, clear the static error
        ' message variable when we reach the entry point.
        If bEntryPoint Then sErrMsg = vbNullString
        bCentralErrorHandler = False
    End If

    'If we're using re-throw error handling,
    'this is not the entry point and we're not debugging,
    're-raise the error, to be caught in the next procedure
    'up the call stack.
    'Procedures that handle their own errors can call the
    'central error handler with bReThrow = False to log the
    'error, but not re-raise it.
    If bReThrow Then
        If Not bEntryPoint And Not gbDEBUG_MODE Then
            On Error GoTo 0
            ERR.Raise lErrNum, sFullSource, sErrMsg
        End If
    Else
        'Error is being logged and handled,
        'so clear the static error message variable
        sErrMsg = vbNullString
    End If

End Function

Answer 1

这是Rob的一本了不起的书。

我的两分钱错误处理（程序或功能）基于 KISS （保持简单愚蠢）

了解你的错误处理程序你想要什么？

这通常是我想要/期望从我的错误处理程序......

1. 发生错误的行
2. 错误编号
3. 错误消息
4. 重置事件（如果适用）

让我们打破上述。你现在已经知道你的错误处理程序是什么样子了，请考虑这个例子。

Sub Sample()
    Dim i As Integer, j As Integer

    On Error GoTo Whoa

    Application.ScreenUpdating = False

    i = 1111111111

    For j = 1 To i
        Debug.Print ThisWorkbook.Sheets(1).Cells(i, 1).Value
    Next i

LetsContinue:
    Exit Sub
Whoa:
    MsgBox Err.Description
    Resume LetsContinue
End Sub

这是一个非常基本的错误处理程序，但它对我来说帮助很小。所以我们现在调整它以使其更有用。如果您运行上面的代码，您会收到一条错误消息，如下面的屏幕截图所示，如果您注意到，它没有多大帮助。



现在让我们解决我在Logic上面提到的所有要点

  

  
1. 发生错误的行
  

有一个名为ERL的属性，很少有人知道。您实际上可以使用它来获取发生错误的代码的行号。为此，您必须确保为代码编号。见这个例子。

Sub Sample()
    Dim i As Integer, j As Integer

10      On Error GoTo Whoa

20      Application.ScreenUpdating = False

30      i = 1111111111

40      For j = 1 To i
50          Debug.Print ThisWorkbook.Sheets(1).Cells(i, 1).Value
60      Next j

LetsContinue:
70      Exit Sub
Whoa:
80      MsgBox Erl
90      Resume LetsContinue
End Sub

当你运行上面的代码时，你会得到这个



所以现在我知道错误发生在第30行i = 1111111111

继续下一步

  

  
1. 错误编号
  
2. 错误消息
  

可以分别从Err.Number和Err.Description检索错误号和错误消息。现在让我们结合Erl，Err.Number和Err.Description

检查此示例

Sub Sample()
    Dim i As Integer, j As Integer

10      On Error GoTo Whoa

20      Application.ScreenUpdating = False

30      i = 1111111111

40      For j = 1 To i
50          Debug.Print ThisWorkbook.Sheets(1).Cells(i, 1).Value
60      Next j

LetsContinue:
70      Exit Sub
Whoa:
80      MsgBox "The Error Happened on Line : " & Erl & vbNewLine & _
           "Error Message : " & Err.Description & vbNewLine & _
           "Error Number : " & Err.Number
90      Resume LetsContinue
End Sub

运行此代码时，您将得到类似的内容。



您可以选择进一步自定义错误消息，使其更加用户友好。例如

'~~> Message you want to deliver to the user in case the error happens
Const sMsg As String = "Please take a screenshot of this message and contact the developer for a resolution"
'~~> Title of your message box
Const sTitle As String = "Oopsie Daisies"

'~~> Change the above as applicable

Sub Sample()
    Dim i As Integer, j As Integer

10      On Error GoTo Whoa

20      Application.ScreenUpdating = False

30      i = 1111111111

40      For j = 1 To i
50          Debug.Print ThisWorkbook.Sheets(1).Cells(i, 1).Value
60      Next j

LetsContinue:
70      Exit Sub
Whoa:
80      MsgBox "The Error Happened on Line : " & Erl & vbNewLine & _
           "Error Message : " & Err.Description & vbNewLine & _
           "Error Number : " & Err.Number & vbNewLine & vbNewLine & _
           sMsg, vbCritical, sTitle
90      Resume LetsContinue
End Sub



到下一个：）

  

重置事件（如果适用）

当您处理事件并发生错误时，如果没有错误处理，则代码会中断。不幸的是，这并没有重置事件。在错误处理程序中重置事件非常重要。

如果您在上面的代码中注意到我们正在设置Application.ScreenUpdating = False。当代码中断时，该事件不会被重置。在这种情况下，您必须在错误处理程序LetsContinue中处理它。见这个例子。

'~~> Message you want to deliver to the user in case the error happens
Const sMsg As String = "Please take a screenshot of this message and contact the developer for a resolution"
'~~> Title of your message box
Const sTitle As String = "Oopsie Daisies"

'~~> Change the above as applicable

Sub Sample()
    Dim i As Integer, j As Integer

10      On Error GoTo Whoa

20      Application.ScreenUpdating = False

30      i = 1111111111

40      For j = 1 To i
50          Debug.Print ThisWorkbook.Sheets(1).Cells(i, 1).Value
60      Next j

LetsContinue:
70      Application.ScreenUpdating = True
80      Exit Sub
Whoa:
90      MsgBox "The Error Happened on Line : " & Erl & vbNewLine & _
           "Error Message : " & Err.Description & vbNewLine & _
           "Error Number : " & Err.Number & vbNewLine & vbNewLine & _
           sMsg, vbCritical, sTitle
100     Resume LetsContinue
End Sub

与Philippe一样，我也强烈建议您使用MZ-Tools进行VBA。我现在一直用它来做驴年......

希望这有帮助。

Answer 2

我需要更多关于这项具体技术的帮助，所以我去了源头，Bovey先生很慷慨地回答。他允许我向StackOverflow社区发布他的回复。

下面的说明是指他首选的“布尔错误处理”技术错误处理方法，而不是备用“重新抛出方法”，两者都在他的“专业Excel开发”第二版中描述。

---

嗨沙里，

在回答有关函数中错误处理的问题时，有 使用VBA中的函数可以使用三种错误处理方案：

1）该函数非常简单，不需要错误处理程序。在里面 不太可能的事件在这样的函数中发生错误它将溢出 进入调用过程的错误处理程序。

2）一个非平凡的函数需要一个错误处理程序并使用布尔返回 书中描述的价值体系。函数需要的任何其他值 return通过ByRef参数返回。这个案子涵盖了绝大多数 我写的功能。有些事情是你无法做到的功能 这个，直接将它们送入另一个函数的参数是一个 例如，但我认为这是一个很好的权衡，以实现子弹 证明错误处理。

3）一个非平凡的函数需要一个错误处理程序，并且必须返回一个值 与其错误状态有关。这是一种罕见的情况，因为我可以转换 通过重构我的代码，将99％以上的这些加入到案例2中。如果你做不到 这个，你唯一的选择是选择一个任意的返回值 正常返回值的范围，并使用它来表示错误 发生了。如果此函数的调用者看到此任意错误标志 它知道它无法继续的价值。

Rob Bovey 应用专业人士 http://www.appspro.com/

---

代码示例（Shari W）

---

' Show how to call a function using this error handling method.
Const giBAD_RESULT As Integer = -1

Function TestMath()   ' An Entry Point

    Dim sngResult As Single
    Dim iNum As Integer

    ' Call the function, actual result goes in sngResult but it returns the error handling boolean.
    ' A true error like Div 0 will go to error handler.

    ' Set Up Error Handling for Entry Point
    Application.EnableCancelKey = xlErrorHandler
    Dim bUserCancel As Boolean
    Const sSOURCE As String = "TestMath()"
    On Error GoTo ErrorHandler
    ' End Error Set Up

    iNum = 0   ' Try 0 to create error
    If Not bDoSomeMath(iNum, sngResult) Then ERR.Raise glHANDLED_ERROR
    ' If function does parameter checking and wants to return a bad input code, check for that.
    If sngResult = giBAD_RESULT Then
        MsgBox ("Bad input to bDoSomeMath " & iNum)
    Else
        MsgBox ("I believe the answer is " & sngResult)
    End If

ErrorExit:
    On Error Resume Next
    Exit Function

ErrorHandler:
    If bCentralErrorHandler(msMODULE, sSOURCE, , True) Then
        Stop
        Resume
    Else
        Resume ErrorExit
    End If
End Function
Function bDoSomeMath(ByVal iNum As Integer, ByRef sngResult As Single) As Boolean

    ' Error handling Set Up
    Dim bReturn As Boolean
    Const sSOURCE As String = "bDoSomeMath()"
    On Error GoTo ErrorHandler
    bReturn = True
    ' End Error Set Up

    If iNum < 0 Or iNum > 1000 Then
        sngResult = giBAD_RESULT   'function failed because I only like the numbers 0 to 1000
        GoTo ErrorExit
    Else
        sngResult = 100 / iNum   ' generate a true error by iNum = 0
    End If

ErrorExit:
    On Error Resume Next
    bDoSomeMath = bReturn
    Exit Function

ErrorHandler:
    bReturn = False
    If bCentralErrorHandler(msMODULE, sSOURCE, , , True) Then
        Stop
        Resume
    Else
        Resume ErrorExit
    End If

End Function

Answer 3

可以找到VBA中错误处理管理的提案here。

完全相同的工具（MZ-Tools）和方法（标准/通用错误处理程序，可用于构建自动错误报告系统）将适用于Excel。