problem on inheritance

[shuisheng]

Dear All,

I have a question on inheritance. Assume I have a base class Vector and
its derived class DecoratedVector as follows:

class Vector
{
// Constructors.
Vector();
Vector(size_t num, double initValue);
Vector(const double *pData, size_t num);
... // Other several constructors.
};

class DecoratedVector : public Vector
{
...

private:
size_t id;
};

The DecoratedVector is in fact a Vector with a decorated id. What I am
wondering is that if there is any way to ease the work of writing the
constructors for class DecoratedVector, since they are always the same
as those in class Vectors.

Thank you for your kind help!

Shuisheng

--
N0 comp.lang.c++, NO my c++ life.

[Victor Bazarov]

shuisheng wrote:

I have a question on inheritance. Assume I have a base class Vector
and its derived class DecoratedVector as follows:

class Vector
{
// Constructors.
Vector();
Vector(size_t num, double initValue);
Vector(const double *pData, size_t num);
... // Other several constructors.
};

class DecoratedVector : public Vector
{
...

private:
size_t id;
};

The DecoratedVector is in fact a Vector with a decorated id. What I am
wondering is that if there is any way to ease the work of writing the
constructors for class DecoratedVector, since they are always the
same as those in class Vectors.

No, there isn't. Constructors are not inherited, so you have to write
all constructor that will have the empty bodies and follow this pattern:

DecoratedVector(type arg) : Vector(arg) {}

V
--
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[Kai-Uwe Bux]

shuisheng wrote:

Dear All,

I have a question on inheritance. Assume I have a base class Vector and
its derived class DecoratedVector as follows:

class Vector
{
// Constructors.
Vector();
Vector(size_t num, double initValue);
Vector(const double *pData, size_t num);
... // Other several constructors.
};

class DecoratedVector : public Vector
{
...

private:
size_t id;
};

The DecoratedVector is in fact a Vector with a decorated id. What I am
wondering is that if there is any way to ease the work of writing the
constructors for class DecoratedVector, since they are always the same
as those in class Vectors.

To some degree, you can use templated constructors:

class DecoratedVector : public Vector {
public:

DecoratedVector ( void ) :
Vector ()
{}

DecoratedVector ( DecoratedVector const & other ) :
Vector ( other )
{}

template < typename A >
DecoratedVector ( A a ) :
Vector ( a )
{}

template < typename A, typename B >
DecoratedVector ( A a, B b ) :
Vector ( a, b )
{}

template < typename A, typename B, typename C >
DecoratedVector ( A a, B b, C c ) :
Vector ( a, b, c )
{}

virtual ~DecoratedVector ( void ) {}

}; // DecoratedVector

This will forward all constructors with up to 3 arguments.
Best

Kai-Uwe Bux