C ++中的好奇重复模板模式(CRTP)的多态集合? [英] A polymorphic collection of Curiously Recurring Template Pattern (CRTP) in C++?

问题描述

我有一个类Base，从中有两个类，如下所述，分别为DerivedA和DerivedB.

I've got a class Base from which I have two classes, DerivedA and DerivedB as defined below.

template <typename Derived>
class Base{
public:
    double interface(){
        static_cast<Derived*>(this)->implementation();
    }
};

class DerivedA : public Base<DerivedA>{
public:
    double implementation(){ return 2.0;}
};

class DerivedB : public Base<DerivedB>{
public:
    double implementation(){ return 1.0;}
};

简而言之，我正在尝试执行以下操作来维护对象的集合，其中有些是DerivedA，有些是DerivedB:

In short, I'm trying to do the following to maintain a collection of objects, some of which are DerivedA and some of which are DerivedB:

std::vector<std::shared_ptr<Derived>>

这显然是不可能的，因为我现在已经将类Derived设置为模板化类.

Which is obviously impossible beacuse I've now made the class Derived a templated class.

有什么方法可以创建/维护对象的多态集合?

Is there any way I can create / maintain a polymorphic collection of objects?

不幸的是，由于在我的实际程序中将函数implementation进行了模板化，所以简单的模板化结构不起作用-因此，implementation将必须是模板化的纯虚函数，而不能是.请原谅我缺乏解释.

Unfortunately, a simple templated structure does not work as the function implementation is templated in my actual program -- so then implementation would have to be a templated pure virtual function, which cannot be. Pardon my lack of explanation.

推荐答案

Alf的建议已达到目标.很容易将其适应您的其他要求.使用纯虚方法定义接口:

Alf's suggestion is on target. It is easy to adapt it to your additional requirement. Define an interface with a pure virtual method:

struct BaseInterface {
    virtual ~BaseInterface() {}
    virtual double interface() = 0;
};

现在，您的模板基类可以从该接口派生:

Now, your template base class can derive from the interface:

template <typename Derived>
class Base : BaseInterface {
public:
    double interface(){
        static_cast<Derived*>(this)->implementation();
    }
};

现在，您可以创建一个指向接口的指针向量:

Now, you can create a vector of pointers to the interface:

std::vector<std::shared_ptr<BaseInterface>>

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