使用纯虚方法克隆C ++类 [英] Cloning C++ class with pure virtual methods

问题描述

我有以下类关系.我想克隆派生类，但出现错误无法实例化抽象类".如何克隆派生类?谢谢.

I have the following relation of classes. I want to clone the class Derived, but I get the error "cannot instantiate abstract class". How I can clone the derived class? Thanks.

class Base {
public:
    virtual ~Base() {}
    virtual Base* clone() const = 0;
};

class Derived: public Base {
public:
    virtual void func() = 0;
    virtual Derived* clone() const {
        return new Derived(*this);
    }
};

推荐答案

只能实例化具体的类.您必须重新设计Derived的接口才能进行克隆.首先，删除 virtual void func()= 0; 之后，您将可以编写以下代码:

Only concrete classes can be instantiated. You have to redesign the interface of Derived in order to do cloning. At first, remove virtual void func() = 0; Then you will be able to write this code:

class Base {
public:
    virtual ~Base() {}
    virtual Base* clone() const = 0;
};

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

另一种解决方案是将纯虚函数保留在原处，并添加一个具体的类:

Another solution is keeping pure virtual function in-place and adding a concrete class:

class Base {
public:
    virtual ~Base() {}
    virtual Base* clone() const = 0;
};

class Derived: public Base {
public:
    virtual void func() = 0;
};

class Derived2: public Derived {
public:
    virtual void func() {};
    virtual Derived2* clone() const {
        return new Derived2(*this);
    }
};

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