What's the Best Way to Handle Data Entry Errors Inside Property Let in VBA

Question

in the Property Let in a ModelClass, I'd like to know what's the best way to advice the client class (ViewClass) about each data entry error.

please, find the ModelClass sample code, as follows:

Option Compare Database
Option Explicit

Private m_idCompra As String

Public Property Get codCompra() As String
    codCompra = m_idCompra
End Property

Public Property Let codCompra(ByVal codigoCompra As String)
    'Data entry roughly treated, just to illustrate.
    If Len(codigoCompra) = 0 Then
        'Advice ViewClass somehow
    ElseIf Not IsNumeric(codigoCompra) Then
        'Advice ViewClass somehow
    'Elseif...
    
    Else
        m_idCompra = codigoCompra
        'Advice ViewClass somehow
    End If
End Property

m_idCompra must be String type, in this case.

thanks in advance.

Answer 1

For similar cases, I add methods like:

Public Function SetCompra(ByVal codigoCompra As String) As Boolean

    Dim Valid As Boolean

    Valid = IsValidCompra(codigoCompra)
    If Valid Then
        ' Set property.
        m_idCompra = codigoCompra
    Else
        ' Raise error or pop message box.
    End If

    SetCompra = Valid

End Function


Public Function IsValidCompra(ByVal codigoCompra As String) As Boolean

    Dim Valid As Boolean

    If <your validation rules> = True Then
        Valid = True
    End If

    IsValidCompra = Valid

End Function