Inheritance base... AGAIN!!!

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I need ... maybe this construction possible????

class OrderHeader
{
....
// method, that passing initialized base class (OrderHeader) into
new Order
public Order ConvertToOrder()
{
return (Order) this;
}

}

class Order : OrderHeader
{
....
}


Can I simply convert base class into inherited class???
Or how to pass initialized base class into new inherited_class ????

Thanks

Mike
 
Hi,

The line :

return (Order) this;

is not possible, it ALWAYS is going to give you error. the thing is that
Order can be used as OrderHeader , but the opposite ( which is what you are
doing ) is NEVER possible.

I think that your problem is more of design, maybe you need composition
instead of inheritance, what if you declare three classes Order ,
OrderHeader , OrderBody and Order has a member of type OrderHeader and
OrderBody ?

Cheers,
 
What do you really want to do by converting base class into inherited
class??
Maybe it's not the correct way...


____________________
Franky
(e-mail address removed)
 
Hi,

I suggest reading a little more about object-oriented programming.
You are violating a very fundamental rule of the OO paradigm.
You can never cast a pointer (or reference) to a class into a pointer (or
reference) to a subclass of that class.
The opposite is ok.

Greetings,

Bram.
 
Hi,
My guess is that you have a list of base classes and your are trying to see
if any of those is a certain derived type.

You have OrderHeader and you want to know if it is of Order type. Say your
code is

class OrderHeader {}

class Order : OrderHeader {}

class OtherOrder : OrderHeader {}

If that is the case you can write code like this

Order order = orderHearder as Order;
if (null != order)
{
// The orderHeader base instance class is actually a Order
instance cast to its base class.

order.MyMethodInOrderClass();
}
else if
{
OtherOrder otherOrder = orderHeader as OtherOrder;
if (null != otherOrder)
{
// The orderHeader base instance class is actually a
OtherOrder instnce cast to its base
otherOrder.MyMethodInOtherOrderClass();
}
}

Hope that helps

--------------------
From: "(e-mail address removed)" <[email protected]>
Subject: Inheritance base... AGAIN!!!
Date: Wed, 28 Jan 2004 15:20:59 +0100
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I need ... maybe this construction possible????

class OrderHeader
{
...
// method, that passing initialized base class (OrderHeader) into
new Order
public Order ConvertToOrder()
{
return (Order) this;
}

}

class Order : OrderHeader
{
...
}


Can I simply convert base class into inherited class???
Or how to pass initialized base class into new inherited_class ????

Thanks

Mike
Click to expand...


Rakesh, EFT.

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