[Mono-list] An inheritance dilemma

[Steve Lessard]

It sounds like what you need is an abstract base class with only a declaration of the SampleMethod method, but no implementation for it.

Obviously I do not know anything about your project, but I do wonder why your code needs to know exactly which type the class is. Isn't that one of the great things about polymorphism?

-SteveL

P.s. Have you tried the typeof operator?


On Nov 22, 2010, at 6:27 AM, Abe Gillespie <abe.gillespie at gmail.com> wrote:

> I've never run into a situation which required inheritance that I
> could not get working with some combo of abstract, virtual, and
> override.  We can only help you as detailed as your example is.  So
> without a better description of the problem this is the best help we
> can offer.
> 
> You most likely don't have to "settle" on a half-baked solution.  And
> your example looks like a rather common use of inheritance.
> 
> Keep thinking about the problem until you find a solution that is 100%
> satisfying.  That or take a little more time to send us a more
> detailed problem description.
> 
> -Abe
> 
> On Mon, Nov 22, 2010 at 9:09 AM, Francisco M. Marzoa <fmmarzoa at gmx.net> wrote:
>> Thanks a lot for your help, Abe.
>> 
>> The previous code was just a simplified version of a more complex one.
>> The fact is that I need each class to have it's own SampleMethod, so it
>> cannot be just removed from B class. And that's the real root of the
>> problem. Obviusly you couldn't know this.
>> 
>> Anyway after look more into this, I've reached the conclussion that
>> there's no chance to obtain the output I want with the class scheme I
>> proposed without, perhaps, dirty hacks based on reflection. And prior
>> doing that, I think it's better to rethink the scheme.
>> 
>> So, the best solution I've found is to rewrite both classes like follows:
>> 
>>    public class A
>>    {
>>        protected string BuildString( string cname )
>>        {
>>            return cname + " method";
>>        }
>> 
>>        public virtual void SampleMethod()
>>        {
>>            Console.WriteLine(this.BuildString("Class A"));
>>        }
>>    }
>> 
>>    public class B : A
>>    {
>>        public override void SampleMethod()
>>        {
>>            base.SampleMethod();
>>            Console.WriteLine(this.BuildString("Class B"));
>>        }
>>    }
>> 
>> 
>> 
>> The key point on this is that as there should be a different
>> SampleMethod overrided in each descendant, we do know within that method
>> the class we're executing in, so we can pass it from there instead of
>> use an instance method GetClassName.
>> 
>> Best regards,
>> 
>> 
>> El 21/11/10 19:53, Abe Gillespie escribió:
>>> I just realized you *really* doing virtualization in GetClassName().
>>> So the better way to do this is:
>>> 
>>> namespace Dummy
>>> {
>>>    class MainClass
>>>    {
>>>        public static void Main (string[] args)
>>>        {
>>>            B b = new B();
>>>            b.SampleMethod();
>>>        }
>>>    }
>>> 
>>>    public class A {
>>>        protected virtual string GetClassName() {
>>>            return "Class A";
>>>        }
>>> 
>>>        public void SampleMethod () {
>>>            Console.WriteLine (GetClassName() + " method");
>>>        }
>>>    }
>>> 
>>>    public class B : A {
>>>        protected override string GetClassName() {
>>>            return "Class B";
>>>        }
>>>    }
>>> }
>>> 
>>> 
>> 
>> 
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