c++ - 从抽象基类调用派生类的c'tor

Question

我有一个数据结构，它在 c'tor 中接受一个抽象类。我想将该类(通过克隆方法)复制到数据结构的私有(private)字段之一，这样我就不必一直将它存储在结构之外。我在 cplusplus.com 上找到了这个解释通过 jsmith:

// Depending upon your needs, you might not require a base class  
// clonable concept.  It would only be needed if you need to store  
// clonable objects polymorphically.  
struct clonable {  
    virtual ~clonable() {}  
    virtual clonable* clone() const = 0;  
};  

class Base : public clonable {  
public:  
    virtual Base* clone() const  
        { return new Base( *this ); }  
};  

class Derived : public Base {  
public:  
     virtual Derived* clone() const  
         { return new Derived( *this ); }  
};

这是我目前所拥有的:

template <class T>
class AbstractBase {
public:
    virtual AbstractBase<T>* clone() const = 0;
    virtual int operator()(const T& lhs, const T& rhs) const = 0;
};

template <class T>
class Derived : public AbstractBase<T> {
public:
    Derived* clone() { return new Derived(*this); } /* ERROR: can't instantiate abstract class */
    int operator()(const T& lhs, const T& rhs) const { return something; }
};

template <class T>
class DataStructure {
public:
    DataStructure(AbstractBase<T>* base) : base(base->clone()) {}
    //...
private:
    AbstractBase<T>* base;
}

我意识到它正在调用 AbstractBase 的 c'tor。有没有一种优雅和/或简单的方法来解决这个问题，同时保持 AbstractBase 抽象？

Answer 1

你需要覆盖

Derived* clone() const;

注意 const。