Object Oriented question

This seems like there is a really basic answer...

I have a collection of objects (lets say Products) inside another object (say Order). The product object has a function called GetTax(). Inside that function it needs to reference a property of its parent object, Order. How can I access a property of a containing object In the below sample, the MyParent object is pseudo-code...

Imports System.Collections.Generic

Public Class Order
Public PaymentMethod As String
Public Products As List(Of Product)

    Public Class Product
        Public Function GetTax() As Decimal
            If MyParent.PaymentMethod = "Cash" Then
                Return 0
            Else
                Return 0.1
            End If
        End Function
    End Class
End Class

Do I need a reference object to the Order I'm missing something.

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Object Oriented question

tj01
Can you tell me how to do this Do I pass it as a reference in the constructor A few lines of code por favor.
*Rick*
I would create a property in the Product class to insert your order and if you ask for the tax of a product and there is no order, throw an exception. Cause if you have a product, it does not necesarely mean you have an order.

Class Product

   Private _order As Order

Public Property Order As Order
    Get
      return _order
    End Get
    Set
      _order = Value
    End Set
End Property

public function GetTax() as Double

    If _order Is Nothing Then
      Throw new Exception("No order")
    End If

    Return _order.GetTax()
End Function

End Class
bschaldon
slabanum wrote:
Really liked your solution, you decoupled both product and order classes and have them look at the PaymentMethod instead. Inversion Of Control principle baby!

I mean Dependency Inversion
distef01
Yes, your Product needs to have a reference to the Order object that contains it.
Dede
Really liked your solution, you decoupled both product and order classes and have them look at the PaymentMethod instead. Inversion Of Control principle baby!

Savannah

I think you need to reconsider how you're doing this. The idea of nesting the order in the product makes me feel a bit irky, and looks a little circular for my liking Big Smile

Perhaps what you could consider is to have the GetTax method accept an argument that specifies a payment type. This could be another object but more simply could be an enumeration. Then, if you needed the total tax for the order, simply iterate throught the contained products, using the payment method enumeration in the method call to sum the tax and return a total.

I don't know how clear that is, so here's my idea in code Big Smile

Imports System.Collections.Generic

Public Enum PaymentMethod
   Cash = 1,
   CreditCard = 2,
   Cheque = 3
End Enum

Public Class Order
    Public PaymentMethod As PaymentMethod = PaymentMethod.Cash
    Public Products As List(Of Product)

   Public Function GetTax() as Double

      Dim dTotalTax as Double = 0

      For Each Product in Products
         dTotalTax += Product.GetTax(Me.PaymentMethod)
      End For

      Return dTotalTax
   End Function
End Class

Public Class Product
        Public Function GetTax(ByVal payMethod as PaymentMethod) As Decimal
            If payMethod = PaymentMethod.Cash Then
                Return 0
            Else
                Return 0.1
            End If
        End Function
End Class

wesam
Thanks slabanum
Object Oriented question

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Object Oriented question

Object Oriented question

tj01

*Rick*

bschaldon

distef01

Dede

Savannah

wesam

Rick