"James Kanze" <ja*********@gmail.com>
???????:11**********************@n2g2000hse.google groups.com...
On Jun 25, 6:25 am, "a" <a...@mail.comwrote:
I have an oop inheritance graph problem.
What is the difference betweent the following 2 inheritance graph?
How does the C++ solve the naming conflict problem for multiple
inheritance
problem?
A
/ \
B C
\ /
D
A A
| |
B C
\ /
D
In the first, you only have a single instance of A; both B and C
have the same instance as their base class. In the second, you
have two instances. In C++, you use virtual inheritance to
achieve the first, e.g.:
First:
class A {} ;
class B : public virtual A {} ;
class C : public virtual A {} ;
class D : public B, public C {} ;
Second:
class A {} ;
class B : public A {} ;
class C : public A {} ;
class D : public B, public C {} ;
Note the presence of the keyword "virtual" in the inheritance in
the first.
I'm not too sure what you mean by "naming conflict". In the
first, there is only one instance of each class, so there is no
ambituity when referring to a base class. In the second, in D
(or when using an object of type D), any direct reference to A
is ambiguous, since the compiler doesn't know which one; to
disabmiguate, first refer to B or C, e.g. B::A::... or C::A::...
--
James Kanze (GABI Software, from CAI) email:ja*********@gmail.com
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Thank you for your reply.
The naming conflict may occur between B and C, since they both inherited
from A. Both B and C have the properties inherited from A, and they have the
same name. So, naming conflict may occurs. I understand the purpose of the
keyword "virtual". But, in terms of "instance", what is the difference
between class B : public virtual A {} and class B : public A {}?
Thanks