Re: OO, Inheritance and Queue


There are 2 ways to solve this.

1, as previously mentioned.. is that you have either an Interface or
abstract class with the method.

public interface IVehicle
void DoSomething()

That would mean that Car, Bicycle and Plane implement this interface (or
abstract class), and write their own implmentations of DoSomething

#2 (which piggy backs off of #1)
If you have the Car Bicycle or Transport objects already, then you can look
at one of these design patterns.
Fascade
Adapter

http://www.dofactory.com/Patterns/Patterns.aspx

I'd probably go Adapter.

The key is that you should never/seldom/only once in a blue moon be writing
case statement checking for object type.
At least you were wise enough to ask, instead of plugging ahead.

...


<query_me2001@xxxxxxxxxxx> wrote in message
news:1154530187.951716.29050@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I have a queue that holds a list of objects with a common base type. As
a simple and contrived example, I have a common type of transportation
methods and derived classes (with there own individual methods which
extend the common base class) of Car, Bicycle and Plane:-

class Car : Transport { OpenWindow(); }
class Bicycle : Transport { RingBell(); }
class Plane : Transport { TakeNap(); }

I want to add each of these classes to the buffer. So I can enqueue
with:

Queue transportQueue;
transportQueue.Enqueue(MyCar);
transportQueue.Enqueue(MyBicycle);
transportQueue.Enqueue(MyPlane);

Now this is where I have got concerns. When I dequeue I do not know
what type has been dequeued.

Transport transportMethod;
transportMethod = (Transport) transportQueue.Dequeue();

When I dequeue, I know that it is a transport class but I do not know
if it is a Car, Bicycle or Plane.

I suppose I could use:
switch (typeof(transportMethod))
{
case Car:
break;
case Bicycle:
break;
case Plane:
break;
}

But this does not seem very Object Oriented and not very maintainable.
Is there a better way of doing this?



.

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