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Is there a way to write an equality test for a VBA class with private members without exposing knowledge of the existence of these private members?

I do a lot of Excel VBA programming, but not many of them are object oriented. Here is something that comes up from time to time that hurts me, and I wonder if there is something that I am missing.

In VBA, let's say I have a C class defined with some private members, for example:

'...

Private hidden1_ As Double
Private hidden2_ As Double

'...

If VBA worked like C ++ or (most?) Other languages ​​that support OOP, I could write a member function to perform an equality test between instances of class C as follows:

'Error: won't compile!
Public Function equal(cinst As C) As Boolean
    equal = (hidden1_ = cinst.hidden1_ And hidden2_ = cinst.hidden2_)
End Function

, VBA, , . , - , , -, :

Public Function equalDef(hidden1 As Double, hidden2 As Double) As Boolean
    equalDef = (hidden1_ = hidden1 And hidden2_ = hidden2)
End Function

Public Function equal(cinst As C) As Boolean
    equal = cinst.equalDef(hidden1_, hidden2_)
End Function

, , .

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EDIT:

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+5
2

, , . OOP VBA, , , ( ) , -. , :

, MyClass ( "C" , "MyClass", .)

, , - , , MyClass, . , IMyClass:

Public Function calcSomething()

End Function

Public Function equal(cinst As IMyClass) As Boolean

End Function

MyClass, :

Implements IMyClass

Private hidden1_ As Double
Private hidden2_ As Double

Public Sub init(h1 As Double, h2 As Double)
    hidden1_ = h1
    hidden2_ = h2
End Sub

Public Function equalDef(hidden1 As Double, hidden2 As Double) As Boolean
    equalDef = (hidden1_ = hidden1 And hidden2_ = hidden2)
End Function

Private Function IMyClass_calcSomething() As Variant
    IMyClass_calcSomething = hidden1_ * hidden2_
End Function

Private Function IMyClass_equal(cinst As IMyClass) As Boolean
    If TypeOf cinst Is MyClass Then
        Dim asMyClass As MyClass
        Set asMyClass = cinst

        IMyClass_equal = asMyClass.equalDef(hidden1_, hidden2_)
    End If
End Function

- , :

Public Function mkMyClass(h1 As Double, h2 As Double) As IMyClass
    Dim ret As MyClass
    Set ret = New MyClass

    Call ret.init(h1, h2)

    Set mkMyClass = ret
End Function

Public Sub useMyClass()
    Dim mc1 As IMyClass
    Set mc1 = mkMyClass(42, 99)

    Dim mc2 As IMyClass
    Set mc2 = mkMyClass(42, 99)

    Dim mc3 As IMyClass
    Set mc3 = mkMyClass(99, 42)

    Debug.Print mc1.calcSomething
    Debug.Print mc1.equal(mc2)

    Debug.Print mc3.calcSomething
    Debug.Print mc3.equal(mc2)
End Sub

"useMyClass" , mc1, mc2 mc3 "init" "equalDef" MyClass. "calcSomething" "equal", .

, , , . , " VBA - PITA (TM)"...

stackoverflow:

VBA,

/ VBA?

+1

,

Private mdhidden1_ As Double
Private mdhidden2_ As Double

Public Property Get hidden1_() As Double

    hidden1_ = mdhidden1_

End Property

Public Property Get hidden2_() As Double

    hidden2_ = mdhidden2_

End Property

Private Sub Class_Initialize()

    'some method of setting variables private to the class
    mdhidden1_ = 1
    mdhidden2_ = 2

End Sub

Public Property Get IsEquivalent(clsCompare As C) As Boolean

    IsEquivalent = Me.hidden1_ = clsCompare.hidden1_ And Me.hidden2_ = clsCompare.hidden2_

End Property

, (Get, Let). IsEquivalent boolean .

+4

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