[RESOLVED] Swapping Objects between Objects and Array of Objects

[kbrizs]

I have the following configuration to create a basic vehicle with an engine.

Interface IEngine

End Interface

Class Vehicle
    Dim VehicleEngine As IEngine

    Public Property Engine() As IEngine
        Get
            Return VehicleEngine
        End Get
        Set(ByVal value As IEngine)
            VehicleEngine = value
        End Set
    End Property

    Sub New()
        Me.Engine = New Engine

    End Sub
End Class

Class Engine
    Implements IEngine

End Class

This is an example of how I instantiate the object.

Dim Police as New Vehicle

This is simple also, but a question starts to come up.

Police.Engine = Nothing

In the above example I destroyed the VehicleEngine object which was created in the constructor when I created the Police object. When this code is complete, the Engine that is destroyed will first be copied into a Garage object. If you are with me so far, I have a quick question. Right now with these examples I am doing the swap manually. Create Object, Copy Object and Destroy Object. Both ways (removing engine and adding engine). Is this the best way to do this, or is there a simpler more efficient way to do the swap.

I have a second question. What would be the best way to create an array of Engines in the above code in the vehicle class instead of just the single engine. So assume that the car can have a hundred engines. What would you alter in the code above to be able to get and set a hundred different engines. I am referring to not have to create a hundred properties but to use one to manage a hundred objects. I definitely could use help with that.

[jmcilhinney]

First up, you aren't destroying anything. Let's say I'm married.

Me.Wife = SomeWoman

Now, I get divorced:

Me.Wife = Nothing

Does that mean that the woman who was my wife was destroyed? Absolutely not. It just means that my Wife property no longer refers to that woman.

The same goes for your code. The fact that you assign Nothing to your Vehicle object's Engine property has no effect whatsoever on the Engine object. For a more specific example, does taking an engine out of a vehicle destroy the engine in real life?

As for your last question, normally you'd use a collection of some sort. There are countless examples of this in the Framework that you use all the time. A DataTable has a Rows property that is a DataRowCollection that contains DataRows. It also has a Columns property that is a DataColumnCollection that contains DataRows. In your case you should define an EngineCollection class that inherits System.Collections.ObjectModel.Collection(Of Engine). Your Vehicle class would then have a ReadOnly Engines property of that type. You can then Add or Remove items from that collection, just as you do with any collection.

[kbrizs]

Ok, thanks