提供基类构造函数

Question

Is it necessary to always provide your base class with a constructor? For example if I had the following base class, and then some derived classes.

class Animal
{
 public:

    //Is this constructor necessary?
    Animal(); 

    virtual ~Animal();
};

class Zebra: public Animal
{
 public:
    Zebra();
   ~Zebra();
};

class Elephant: public Animal
{
 public:
    Elephant();
   ~Elephant();
};

Assuming that I am creating Animal pointers and then dynamically allocating new Zebra and Elephant objects. If I never intend to create an Animal object, then is there any actual need to explicitly create an Animal constructor?

Answer 1

You don't need to explicitly provide constructor. A default one is generated (if you don't provide other constructor).

so

class Animal
{
public:

    virtual ~Animal();
};

is sufficient.

Derived classes constructors would call Base class constructor (explicitly of implicitly).