C++ 多态Clone方法的模板化实现方式笔记-优快云博客

本文链接：https://blog.youkuaiyun.com/MCCreeper/article/details/137303527

本文介绍了C++中的Cloneable模板如何用于创建派生类的克隆方法，以及C++11后通过unique_ptr改进实现的方式，重点提及了CuriouslyRecurringTemplatePattern(CRTP)的概念和应用实例。

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直接上模板工具类：

template <typename Base, typename Derived>
class Cloneable : public Base
{
public:
    using Base::Base;
 
    virtual Base *clone() const
    {
        return new Derived(static_cast<Derived const &>(*this));
    }
};

使用方法示例：
基类Vehicle

class Vehicle
{
protected:
    int fuelCapacity;
 
public:
    Vehicle() {};
    Vehicle(int fuelCapacity) : fuelCapacity(fuelCapacity) {};
    virtual ~Vehicle() {};
    virtual Vehicle *clone() const = 0;
 
    virtual void describe() const = 0;
};

一级子类Plane，使用了Cloneable模板生成了clone方法：

class Plane : public Cloneable<Vehicle, Plane>
{
private:
	typedef Cloneable<Vehicle, Plane> BaseClass;
 
protected:
	int wingSpan;
 
public:
	Plane() {};
	Plane(int fuelCapacity, int wingSpan) : BaseClass(fuelCapacity), wingSpan(wingSpan) {};
 
	virtual void describe() const
	{
 		std::cout << "I am a plane" << std::endl;
	}
};

二级子类FighterPlane，同样也能使用Cloneable模板生成clone方法：

class FighterPlane : public Cloneable<Plane, FighterPlane>
{
private:
	typedef Cloneable<Plane, FighterPlane> BaseClass;
 
protected:
	int numberOfBombs;
 
public:
	FighterPlane() {};
	FighterPlane(int fuelCapacity, int wingSpan, int numberOfBombs)
 	: BaseClass(fuelCapacity, wingSpan), numberOfBombs(numberOfBombs) {};
 
	virtual void describe() const
	{
		std::cout << "I am a fighter plane" << std::endl;
	}
};