Is it possible to use stdSentry to release the memory of a routine ?

[gagota]

First of all, I really appreciate your work, I find what you managed to do with vba really amazing ! It's helping me at my work. I will maybe contribute to this project in the future :)

I would like to write something like

Sub Fun_Clean(ByRef col)
    Set col = Nothing
End Sub

Sub Fun()
    Dim col As New Collection

    Dim factory As stdSentry: Set factory = ' ...
    With factory()
        ' Do stuff that can raise an error
    End With
End Sub

I want the routine to always run the cleaning section, even if an error is raised. It's mostly needed for when I open a workbook or recordset and I need to close it.

Also, is the "stdSentry" class ready to be used ? It's not mentioned in the roadmap so I assumed it was ready since it's not in the "WIP" folder. But then I saw that it uses stdError that is WIP so it makes me doubt it...

[sancarn]

Hi Gagota,

I'm not at my PC, but I will try to respond to this. Thanks for the interest and I'm glad to here this is useful at your work :)

First off, the stdSentry class is absolutely ready to use, no worries there at all! I need to update the readme probably... It does have a method in it which utilises stdError, but you absolutely don't have to use that method. It's there purely if you ever do also have stdError within your module, and it's built for building stack traces basically. Critically the module doesn't have Option Explicit so it won't compiler error when the function is never called, however it will runtime error if you don't include stdError in your project.

Contributions are absolutely welcome too as long as they fit the style of the repo! However if it is merely a project which uses stdVBA, this can be contributed to the examples repo!

Now to the substance. Typically I would avoid what you are suggesting (in the case of a collection) and opt for:

With New Collection
  ...
End With

As soon as the collection goes out of scope (i.e. not within the With-block) it will be set to nothing, triggering any uninitialisers or whatever. However I assume there is method to your madness in your specific situation hehe.

I think you could probably do something like this:

Dim col as collection
Public Sub test
  Dim factory as stdSentry: set factory = setNothingOnExpire()
  set col = new Collection
  With factory(col)
    ...
  End With
  debug.print col is nothing
End Sub
Public Function SetNothingOnExpire() as stdSentry
  Dim onInit as stdCallback: set onInit = stdCallback.CreateFromMethod("","null_method")
  Dim onDestroy as stdCallback: set onDestroy = stdCallback.CreateFromMethod("", "obj_set_to_nothing")
  set setNothingOnExpire = stdSentry.Create(onInit, onDestroy)
End Function
Sub null_method(ParamArray v())
End Sub
Sub obj_set_to_nothing(ByVal obj as object)
  set obj = nothing
End Sub

This is untested, but I think it should do what you are after...

However:

even if an error is raised

Error handling in VBA is weird... I think when an error is raised the jump doesn't exit the with block... I might be wrong, but that's my recollection? However when the function itself goes out of scope, it absolutely will execute the cleanup if it's within a sentry object. So this will probably be good enough for your needs I imagine? Unless your user clicks End.

Typically the pattern I use can be seen in the stdError-enwrapped branch of the repo for instance:

Public Function CreateFromArray(ByVal arr As Variant) As stdArray
  With stdError.getSentry("stdArray#CreateFromArray", "arr", arr)
    On Error GoTo stdErrorWrapper_ErrorOccurred
    
        Set CreateFromArray = New stdArray
        
        Dim i As Long
        Dim lb As Long: lb = LBound(arr)
        Dim ub As Long: ub = UBound(arr)
        Call CreateFromArray.protInit(ub - lb + 1, 10)
        
        For i = lb To ub
            Call CreateFromArray.Push(arr(i))
        Next
    
        'Raise AfterCreate event
        RaiseEvent AfterCreate(Create)
    
    Exit Function
    stdErrorWrapper_ErrorOccurred:
      Call Err_Raise(Err.Number, Err.Source, Err.Description)
  End With
End Function
...
Private Sub Err_Raise(ByVal number as Long, Optional ByVal source as string = "", Optional ByVal description as string = "")
  Call stdError.Raise(description)
End Sub

stdError allows you to provide a custom error handler for all errors, where you can specify that you want to e.g. msgbox, without giving the user the opportunity to fully end runtime