I have a base class Foo that I have defined as abstract. Derived from this is class Bar. I get an error compiling Foo as it's construcotr has a method body. This is what I am trying to do :-

abstract class Foo {
    protected int a;

    this( int a ) {
        this.a = a;
    }
}

class Bar : Foo {
    this ( int a ) {
        super ( a );
    }
}

Is this supposed to fail in D ?

Okay so I should make the variable private in Foo :o)

However, the question remains.

"Don Stewart" <donald.m.stewart@btinternet.com> wrote in message news:acgvf6$1hou$1@digitaldaemon.com...
> I have a base class Foo that I have defined as abstract. Derived from this is class Bar. I get an error compiling Foo as it's construcotr has a
method
> body. This is what I am trying to do :-
>
> abstract class Foo {
>     protected int a;
>
>     this( int a ) {
>         this.a = a;
>     }
> }
>
> class Bar : Foo {
>     this ( int a ) {
>         super ( a );
>     }
> }
>
> Is this supposed to fail in D ?
>
>

"Don Stewart" <donald.m.stewart@btinternet.com> wrote in message news:acgvf6$1hou$1@digitaldaemon.com...
> I have a base class Foo that I have defined as abstract. Derived from this is class Bar. I get an error compiling Foo as it's construcotr has a
method
> body. This is what I am trying to do :-
>
> abstract class Foo {
>     protected int a;
>
>     this( int a ) {
>         this.a = a;
>     }
> }
>
> class Bar : Foo {
>     this ( int a ) {
>         super ( a );
>     }
> }
>
> Is this supposed to fail in D ?
>



Mmm...
I thought abstract classes should have no
implementation? I know it is possible
to do this in C++, but why it should be
done I don't understand...
Do you want to force the programmer deriving
a class from Foo to implement certain
functions? Then why not make just the
functions abstract?

On another note you might want to look
into interfaces as a substitute for
Abstract Base Classes in D...


--
Stijn
OddesE_XYZ@hotmail.com
http://OddesE.cjb.net
_________________________________________________
Remove _XYZ from my address when replying by mail

"OddesE" <OddesE_XYZ@hotmail.com> wrote in message news:acjm92$137a$2@digitaldaemon.com...
> "Don Stewart" <donald.m.stewart@btinternet.com> wrote in message news:acgvf6$1hou$1@digitaldaemon.com...
> > I have a base class Foo that I have defined as abstract. Derived from
this
> > is class Bar. I get an error compiling Foo as it's construcotr has a
> method
> > body. This is what I am trying to do :-
> >
> > abstract class Foo {
> >     protected int a;
> >
> >     this( int a ) {
> >         this.a = a;
> >     }
> > }
> >
> > class Bar : Foo {
> >     this ( int a ) {
> >         super ( a );
> >     }
> > }
> >
> > Is this supposed to fail in D ?
> >
>
>
>
> Mmm...
> I thought abstract classes should have no
> implementation? I know it is possible
> to do this in C++, but why it should be
> done I don't understand...
> Do you want to force the programmer deriving
> a class from Foo to implement certain
> functions? Then why not make just the
> functions abstract?

Because I want to create a class that has fields and methods that can manipulate the fields BUT not the class to be new'ed.

Only derived classes can be newed.

It's in C++, it's in Java, I wondered why it was not in D.

An interface would mean I have to add the fields to all implementing classes rather than using the base class.


>
> On another note you might want to look
> into interfaces as a substitute for
> Abstract Base Classes in D...
>
>
> --
> Stijn
> OddesE_XYZ@hotmail.com
> http://OddesE.cjb.net
> _________________________________________________
> Remove _XYZ from my address when replying by mail
>
>
>
>

"Don Stewart" <donald.m.stewart@btinternet.com> wrote in message news:ackskg$2b2m$1@digitaldaemon.com...

> Because I want to create a class that has fields and methods that can manipulate the fields BUT not the class to be new'ed.

Just declare its constructor as private. It is the way it was done in C++, and I think it should be done so in D as well.

Abstract class is a class with all members abstract. If you only
want to define some of the members abstract, just use the "abstract"
attributes on them. You still can't create such class, but you
can define bodies for non-abstract methods.

Yes of course. I seen the years of Java have killed off the C++ brain cells :o)

My brain hasn't managed to context switch yet LOL

Don
"Pavel Minayev" <evilone@omen.ru> wrote in message
news:acl7ni$4ed$1@digitaldaemon.com...
> "Don Stewart" <donald.m.stewart@btinternet.com> wrote in message news:ackskg$2b2m$1@digitaldaemon.com...
>
> > Because I want to create a class that has fields and methods that can manipulate the fields BUT not the class to be new'ed.
>
> Just declare its constructor as private. It is the way it was done in C++, and I think it should be done so in D as well.
>
> Abstract class is a class with all members abstract. If you only
> want to define some of the members abstract, just use the "abstract"
> attributes on them. You still can't create such class, but you
> can define bodies for non-abstract methods.
>
>