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Rob Nicholso
#1 / 21
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 Multiple inheritence? Did I hear somewhere what VB.Net won't support multiple inheritance? So two Inherits in a class won't be allowed? Cheers, Rob.
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| Mon, 09 Jun 2003 01:05:41 GMT |
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Tomas Restrep
#2 / 21
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Multiple inheritence? Rob, Quote: > Did I hear somewhere what VB.Net won't support multiple inheritance? So
two
> Inherits in a class won't be allowed?
That's correct. The .NET object model only supports single inheritance, so neither C# not MC++ support it. You can still implement multiple interfaces, though, like in Java. --
Tomas Restrepo [VC++ MVP]
http://www.mvps.org/windev/
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| Mon, 09 Jun 2003 01:56:14 GMT |
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Mattias Sj?gr
#3 / 21
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Multiple inheritence? Quote: >You can still implement multiple interfaces, though, like in Java.
And an interface can derive from multiple base interfaces. Matt
============================================
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| Mon, 09 Jun 2003 02:06:28 GMT |
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Rob Nicholso
#4 / 21
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Multiple inheritence? Quote: > And an interface can derive from multiple base interfaces.
Hmm, so let me get my head around this. In C++, I can do things like: public AdverseEvent : public Object, public Procedure
{
// etc
Quote: };
In that AdverseEvent inherits both the members from Object and Procedure. This isn't allowed in .NET?
Cheers, Rob.
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| Mon, 09 Jun 2003 02:28:13 GMT |
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Sjoerd Verwe
#5 / 21
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Multiple inheritence? Quote: >public AdverseEvent : public Object, public Procedure
>This isn't allowed in .NET?
Not in managed code (using the CLR). However, you can still write unmanaged C++ code with all the C++ horrors using VS.NET if you want.
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| Mon, 09 Jun 2003 02:37:15 GMT |
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Rob Nicholso
#6 / 21
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Multiple inheritence? Quote: > Not in managed code (using the CLR). However, you can still write
> unmanaged C++ code with all the C++ horrors using VS.NET if you want.
What's so bad about multiple inheritance? Rob.
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| Mon, 09 Jun 2003 03:22:10 GMT |
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Sjoerd Verwe
#7 / 21
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Multiple inheritence? Quote: > What's so bad about multiple inheritance?
Inherently, not all that much. It just opens up a whole new world of coding errors and bugs. Most new languages intentionally do not support it.
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| Mon, 09 Jun 2003 03:29:31 GMT |
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Marcu
#8 / 21
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Multiple inheritence? I don't know but MS don't allow it in the CLR. I think they should allow it too. - Marcus
Quote: > > Not in managed code (using the CLR). However, you can still write > > unmanaged C++ code with all the C++ horrors using VS.NET if you want. > What's so bad about multiple inheritance?
> Rob.
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| Mon, 09 Jun 2003 03:29:33 GMT |
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Jonathan Alle
#9 / 21
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Multiple inheritence? Quote: > What's so bad about multiple inheritance?
Naming clashes are a big thing. The Syntax to resolve them tends to be atrocious. MI is used mainly with abstract classes to show what the can do. Interfaces
take on this role in a more elegant fashion. For instance, the enumerator in
by Z-Tree works completely different from a standard B-Tree, so inheriting
Enumerator would be silly. However I still need the follow a contract in
order to communicate with the For Each structure. This is where interfaces
come into play. It describes what my class can do, not how it does it.
--
Jonathan Allen
Quote: > > Not in managed code (using the CLR). However, you can still write > > unmanaged C++ code with all the C++ horrors using VS.NET if you want. > What's so bad about multiple inheritance?
> Rob.
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| Mon, 09 Jun 2003 03:57:49 GMT |
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Adam D. Barrat
#10 / 21
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Multiple inheritence? Quote:
> > Not in managed code (using the CLR). However, you can still write > > unmanaged C++ code with all the C++ horrors using VS.NET if you want. > What's so bad about multiple inheritance?
Imagine you have three classes, A, B and C: Class A {
public doSomething( int )
public doSomethingElse()
Quote: }
Class B { public doSomething( int ) public doYetAnotherThing() Quote: }
Class C Inherits From A, B If you create an instance of C and then call doSomething() on that instance,
are you calling A.doSomething() or B.doSomething()?
--
Adam D. Barratt
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| Mon, 09 Jun 2003 06:40:26 GMT |
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Alex Moran
#11 / 21
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Multiple inheritence? Yes, but in that instance, you'll get a compiler error with the infamous "Ambiguity in function xxxx" at least in VC6++
Quote:
> > > Not in managed code (using the CLR). However, you can still write > > > unmanaged C++ code with all the C++ horrors using VS.NET if you want. > > What's so bad about multiple inheritance?
> Imagine you have three classes, A, B and C:
> Class A {
> public doSomething( int )
> public doSomethingElse()
> }
> Class B {
> public doSomething( int )
> public doYetAnotherThing()
> }
> Class C Inherits From A, B
> If you create an instance of C and then call doSomething() on that
instance,
> are you calling A.doSomething() or B.doSomething()?
> --
> Adam D. Barratt
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| Mon, 09 Jun 2003 07:24:25 GMT |
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Marcu
#12 / 21
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Multiple inheritence? Yes, that's a big problem because e.g. Dispose is a function that exists in the most classes in the CLR. Maybe we should type A.doSomething() instead of just doSomething()?
- Marcus
Quote:
> > > > Not in managed code (using the CLR). However, you can still write > > > > unmanaged C++ code with all the C++ horrors using VS.NET if you want. > > > What's so bad about multiple inheritance?
> > Imagine you have three classes, A, B and C:
> > Class A {
> > public doSomething( int )
> > public doSomethingElse()
> > }
> > Class B {
> > public doSomething( int )
> > public doYetAnotherThing()
> > }
> > Class C Inherits From A, B
> > If you create an instance of C and then call doSomething() on that
> instance,
> > are you calling A.doSomething() or B.doSomething()?
> > --
> > Adam D. Barratt
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| Mon, 09 Jun 2003 08:46:01 GMT |
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Rob Nicholso
#13 / 21
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Multiple inheritence? Quote: > Maybe we should type A.doSomething() instead of just doSomething()?
Yes, that's sensible. Isn't it A::doSomething() in C++ parlance? Cheers, Rob
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| Tue, 10 Jun 2003 01:04:36 GMT |
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Rob Nicholso
#14 / 21
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Multiple inheritence? Quote: > If you create an instance of C and then call doSomething() on that
instance,
> are you calling A.doSomething() or B.doSomething()?
The same can be said of every single name in the entire system. I create an component Object called Wibble and you create another component called Wibble. We reference them and do dim MyObj as Wibble
Which object are we referring. Fully qualifying declarations is just name of
the game. Blocking MI just because of this sounds like a knee jerk reaction.
dim MyObj as RobNicholson.Wibble
isn't *that* bad is it?
The same with inheritence. If I have to write
inherits ClassA
inherits ClassB
ClassA.DoSomething
ClassB.DoSomething
It's not much different is it?
Cheers, Rob.
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| Tue, 10 Jun 2003 01:03:54 GMT |
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Rob Nicholso
#15 / 21
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Multiple inheritence? Quote: > MI is used mainly with abstract classes to show what the can do.
Interfaces take on this role in a more elegant fashion. For instance, the enumerator in The problem I have with interfaces is that it creates an awful lot more
typing in VB (unless VB.Net is going to do this another way). In our system,
we have our own object and have a:
Implements IObject
In most classes. But then each object has to manually implement each of the
members with the not-so-nice syntax:
sub IObject_Save()
In most circumstances, we usually delegate a lot of the code in the
interface to a "helper" object that implements the code so we end up with:
private m_Object as new CObject
sub IObject_Save()
m_Object.Save
end sub
And if we decide to add, change or delete an interface, we have to go
through every object that users the interface. Not nice.
So at least we'll be able to inherit CObject in this case, but an object
often uses other interfaces/objects as well.
Cheers, Rob.
Quote: > by Z-Tree works completely different from a standard B-Tree, so inheriting > Enumerator would be silly. However I still need the follow a contract in > order to communicate with the For Each structure. This is where interfaces > come into play. It describes what my class can do, not how it does it. > --
> Jonathan Allen
> > > Not in managed code (using the CLR). However, you can still write
> > > unmanaged C++ code with all the C++ horrors using VS.NET if you want.
> > What's so bad about multiple inheritance?
> > Rob.
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| Tue, 10 Jun 2003 01:08:35 GMT |
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