470,870 Members | 1,120 Online

oop inheritance graph

Hi,
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?

Thanks

A
/ \
B C
\ /
D
A A
| |
B C
\ /
D
Jun 25 '07 #1
5 3342
On Jun 24, 11:25 pm, "a" <a...@mail.comwrote:
Hi,
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?

Thanks

A
/ \
B C
\ /
D

A A
| |
B C
\ /
D
There is no difference between the two graphs that you draw since both
B and C inherit from A in both graphs. You have to use "virtual
inheritance" for class A. Scott Meyers discusses this point in detail
in his book Effective C++ (item 43). You may want to avoid this kind
of inheritance graph. The naming convention is defined by the closest
definition of a function to D. For example, if A defines foo() and
this is redefined in C, D uses the C version of foo(). Hope it helps.

Jun 25 '07 #2
a wrote:
Hi,
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?

Thanks

A
/ \
B C
\ /
D
A A
| |
B C
\ /
D

http://www.parashift.com/c++-faq-lit...heritance.html

--
Sumit Rajan <su*********@gmail.com>
Jun 25 '07 #3
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
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34

Jun 25 '07 #4
aaragon wrote:
On Jun 24, 11:25 pm, "a" <a...@mail.comwrote:
>Hi,
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?

Thanks

A
/ \
B C
\ /
D

A A
| |
B C
\ /
D

There is no difference between the two graphs that you draw since both
B and C inherit from A in both graphs. You have to use "virtual
inheritance" for class A. Scott Meyers discusses this point in detail
in his book Effective C++ (item 43). You may want to avoid this kind
of inheritance graph. The naming convention is defined by the closest
definition of a function to D. For example, if A defines foo() and
this is redefined in C, D uses the C version of foo(). Hope it helps.
No, you don't "have to" use virtual inheritance. That's the difference
between them: the top one uses it and the bottom one doesn't.

--

-- Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com)
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (www.petebecker.com/tr1book)
Jun 25 '07 #5

"James Kanze" <ja*********@gmail.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
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34

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

Jun 26 '07 #6