VB6中的集中式错误处理 [英] Centralized error handling in VB6

问题描述

 公共函数ToError（strClass As String，strMethod As String ）As String 
 
错误GoTo errHandle 
 
 ToError =Err&错误编号& _ 
，Src：& Err.Source& _ 
，Dsc：&错误描述& _ 
，Project：& App.Title& _ 
，Class：& strClass& _ 
，方法：& strMethod& _ 
，行：& Erl 
 
 Err.Clear 
 
退出点：$ b​​ $ b退出函数
 
 errHandle：
 oLog.AddToLogToError方法中的错误：& Err.Description，False 
恢复exitPoint 
结束功能
  

事实证明因为我在这个函数中声明一个错误处理程序 On Error GoTo errHandle ，VB6在我能够记录之前清除错误。

有没有办法阻止On Error GoTo errHandle语句清除错误？

解决方案

一个错误语句将永远清除 Err 变量（ Erl 也将重置为0）。在理论上，这意味着您可以通过将 On Error 语句移到 ToString = ... 行（<或删除 ToError 函数中的错误处理程序），但不幸的是，这不一定总是有效。

您的项目引用的每个组件（DLL，ActiveX EXE等）基本上在内存中都有自己的 Err 实例。因此，如果您的 MainApp.exe 引发了一个错误，该错误传递给 ToError （驻留在单独的 ErrorHandling.dll ），DLL将不会看到您的EXE看到的 Err 变量。他们每个都有自己的私人 Err 变量。

有一个关于问题的至少两种方法，我可以想想：

方法1

As Zian Choy提到的，您可以在 ToError 函数中添加其他参数，一个

代码 / p>

 公共函数ToError（_ 
 ByVal strErrSource As String，_ 
 ByVal nErrNumber As Long，_ 
 ByVal sErrDescription As String，_ 
 ByVal nLineNumber As Long）As String 
  

使用示例

然后，您必须像这样从错误处理程序中调用此类代码，将当前 Err 对象，以及 Erl ：

  ToError Err.Source，Err.Number，Err.Description，Erl 
  / pre> 
 
 
如果您还想要 App.Title ，您将不得不添加一个附加参数 ToError ，因为 App.Title 将等于 App.Title定义 ToError 方法的项目，而不是引发错误的组件。如果 ToError 在另一个项目中，这很重要。
 
 
 
方法2 
 
 
 
您可以通过将 Err 对象本身传递为一个更少的详细信息，使您的 ToError 函数的参数，但是在这种情况下，您的 ToError 函数的第一件事情是立即存储所需的所有相关属性的副本，因为后续的 On Error 语句将清除该变量。
 
 
 
 代码 
 
 $ b $公共函数ToError（ByVal oError As ErrObject，ByVal nLineNumber As Long）As String 
 
'首先复制重要的Err属性'
 '在做任何事情之前...'
 
 Dim strErrSource As String 
 Dim nErrNumber As Long 
 Dim strErrDescription As String 
 
 strErrSource = oError.Source 
 nErrNumber = oError.Number 
 strErrDescription = oError.Description 
 
错误Goto errHandle 
 
'更多代码这里
'... 
  

使用示例

  ToError Err，Erl 
  

I have the following method that all the error handlers call:

Public Function ToError(strClass As String, strMethod As String) As String

    On Error GoTo errHandle

    ToError = "Err " & Err.Number & _
                      ", Src: " & Err.Source & _
                      ", Dsc: " & Err.Description & _
                      ", Project: " & App.Title & _
                      ", Class: " & strClass & _
                      ", Method: " & strMethod & _
                      ", Line: " & Erl

    Err.Clear

exitPoint:
   Exit Function

errHandle:
   oLog.AddToLog "Error in ToError Method: " & Err.Description, False
   Resume exitPoint
End Function

It turns out that because I declare an error handler in this function On Error GoTo errHandle, VB6 clears the error before I am able to record it.

Is there a way to prevent the 'On Error GoTo errHandle' statement from clearing the error?

解决方案

An On Error statement will always clear the Err variable (Erl will also be reset to 0). In theory this means you could fix the problem by moving the On Error statement below the ToString = ... line (or removing the error handler in the ToError function altogether), but unfortunately that won't necessarily always work either.

Each component (DLL, ActiveX EXE, etc.) referenced by your project essentially gets its own Err instance in memory. So, if your MainApp.exe raises an error which gets passed to ToError (residing in a separate ErrorHandling.dll for example), the DLL won't see the Err variable that your EXE sees. They each have their own private Err variables.

There are a at least two ways around the problem that I can think of:

Method 1

As Zian Choy mentions, you could add additional parameters to your ToError function, one for each property of the Err object that you need access to.

Code

Public Function ToError( _
   ByVal strErrSource As String, _
   ByVal nErrNumber As Long, _
   ByVal sErrDescription As String, _
   ByVal nLineNumber As Long) As String

Example usage

You would then have to call like this from your error handlers like so, passing it all the relevant values from the current Err object, along with Erl:

ToError Err.Source, Err.Number, Err.Description, Erl 

If you also want App.Title, you're going to have to add an additional parameter to ToError for that as well, since App.Title will be equal to the App.Title of the project where the ToError method is defined, not the component where the error was raised. This is important if ToError is in a different project.

Method 2

You can make your ToError calls a little less verbose by passing the Err object itself as a parameter to the function, however the first thing your ToError function should do in this case is immediately store a copy of all the relevant properties you need since a subsequent On Error statement will clear the variable.

Code

Public Function ToError(ByVal oError As ErrObject, ByVal nLineNumber As Long) As String

   'Copy the important Err properties first, '
   'before doing anything else...            '

   Dim strErrSource As String
   Dim nErrNumber As Long
   Dim strErrDescription As String

   strErrSource = oError.Source
   nErrNumber = oError.Number
   strErrDescription = oError.Description

   On Error Goto errHandle

   'More code here
   '...

Example Usage

ToError Err, Erl

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