Implements in VBA

[tiredofit]

Looking at the article:

https://stackoverflow.com/questions/24510264/vba-difference-between-public-variable-and-property

I have a couple of questions.


This is a standard module:

Sub Main()

    Dim myAccount As Account
    Set myAccount = New Account

    Debug.Print "Starting Balance: " & myAccount.Balance

    myAccount.Deposit (2000)
    Debug.Print "Deposited: 2000"

    myAccount.WithDraw (250)
    Debug.Print "Withdrew: 250"

    Debug.Print "Ending Balance: " & myAccount.Balance

    ' can't set balance
    ' myAccount.Balance = 999999999999999999999999
End Sub

This is the class Account:

Implements IAccountServices

' balance should be private
' cause you should only have a getter for it
' you should only be able to set the balance inside this class
' based on the operations
Private accBalance As Double

' see Getter only - no setter
Public Property Get Balance() As Double
    Balance = accBalance
End Property

Public Function Deposit(amount As Double)
    accBalance = accBalance + amount
End Function

Public Function WithDraw(amount As Double)
    accBalance = accBalance - amount
End Function

Private Sub IAccountServices_Deposit(amount As Double)
    accBalance = accBalance + amount
End Sub

Private Sub IAccountServices_WithDraw(amount As Double)
    accBalance = accBalance - amount
End Sub

This is the class IAccountServices:

Private Sub IAccountServices_Deposit(amount As Double)
    accBalance = accBalance + amount
End Sub

Private Sub IAccountServices_WithDraw(amount As Double)
    accBalance = accBalance - amount
End Sub

In class Account, shouldn't these two functions be Subs?

Public Function Deposit(amount As Double)
    accBalance = accBalance + amount
End Function

Public Function WithDraw(amount As Double)
    accBalance = accBalance - amount
End Function

Also because Implements has been added to the class Account, these two Subs are required:

Private Sub IAccountServices_Deposit(amount As Double)
    accBalance = accBalance + amount
End Sub

Private Sub IAccountServices_WithDraw(amount As Double)
    accBalance = accBalance - amount
End Sub

but I can't see where they're used, so wouldn't it be better to remove the word Implements, as well as these two Subs?

Thanks

 

[RoryA]

I would make them subs since they don't return anything, but there's no reason you have to.

You only use Implements if you want to use an interface. That code doesn't actually use the interface at all, so it serves no real purpose there.

 

[tiredofit]

I would make them subs since they don't return anything, but there's no reason you have to.

You only use Implements if you want to use an interface. That code doesn't actually use the interface at all, so it serves no real purpose there.

Thought so, thanks.

I was taught "The rule" - functions CAN return a value (but don't have to). But if you're not going to return a value why confuse people. Just make them a Sub!