Re: Inheirting constructor?

From:

"Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 12 Nov 2010 16:40:02 +0100

Message-ID:

<ibjn4j$hol$1@news.eternal-september.org>

* Steve Keller, on 12.11.2010 15:17:

Is is possible to inherit a constructor? I have an abstract base
class with lots of derived classes.

class Base {
protected:
    int a, b;
public:
    Base(int a, int b) : a(a), b(b) {}
    virtual int foo() = 0;
};

class A : public Base {
public:
    A(int a, int b) : Base(a, b) {}
    virtual int foo();
};

int A::foo()
{
    // do something with a and b
    return a + b;
}

Since I have lots of classes derived from Base it gets tedious to
write all the constructors for the derived classes. Is is possible to
skip the definition of A::A(int a, int b) and have it some inherited
automatically from Base?

C++0x may add the capability of inheriting constructors. As I understand there
is some discussion about removing that feature, because argument forwarding can
express (in a verbose & inconvenient way) most of the cases. But anyway, there's
no such thing in C++98.

If the problem is lots of arguments, then consider defining argument packs. Then
each derived class constructor has at most one or two arguments. :-)

I can imagine that with proper argument pack type naming that also helps with
clarity for the code that instantiates objects of the classes.

Cheers & hth.,

- Alf

--
blog at <url: http://alfps.wordpress.com>