Protected

Declares a class member (variable, procedure, or property) that is accessible from inside the declaring class and from classes that derive from it via Inherits, but not from outside callers.

Note

The Protected access modifier is a twinBASIC extension over classic VBA, which has only Public, Private, and Friend. Protected is meaningful only inside an Inherits hierarchy; in a class without inheritance, it behaves like Private.

Syntax:

  • Protected varname [ ( [ subscripts ] ) ] [ As [ New ] type ] [ , varname … ]

  • Protected [ Overridable ] Sub | Function | Property Get | Property Let | Property Set name …

In a variable declaration, Protected has the same form as Private/Public: a comma-separated list of names with optional WithEvents/New and As-clause. Protected is valid only at class scope; it cannot be used inside a procedure (use Dim or Static), and it cannot be used in a Module (modules have no notion of derived types).

In a procedure declaration, Protected replaces the Public/Private/Friend modifier. Combined with the Overridable keyword, it declares an inheritance hook — a method or property that derived classes are allowed to override.

Visibility summary

Modifier Same class Derived class (via Inherits) Other code
Public yes yes yes
Friend yes yes within the project only
Protected yes yes no
Private yes no no

Example

The following pattern uses Protected state plus an Overridable Protected method as an inheritance hook. The base Animal class exposes a public Speak that delegates to GetSound, which derived classes override:

Private Class Animal
    Protected _name As String
    Protected _dob As Date  ' date of birth

    Public Sub New(name As String, dob As Date)
        _name = name
        _dob = dob
    End Sub

    Public Property Get Name() As String
        Name = _name
    End Property

    Public Sub Speak()
        Debug.Print _name & " says: " & GetSound()
    End Sub

    ' Overridable hook for derived classes.
    Protected Overridable Function GetSound() As String
        GetSound = ""
    End Function
End Class

Private Class Dog
    Inherits Animal

    Public Sub New(name As String, dob As Date)
        Animal.New(name, dob)               ' explicit base constructor call
    End Sub

    Protected Function GetSound() As String Overrides Animal.GetSound
        GetSound = "woof"
    End Function
End Class

_name and _dob are visible inside Dog (because Dog inherits from Animal), but not visible to any code that holds an Animal or Dog reference from outside the hierarchy.

See Also