问题描述

如果我有一个带有模板的类:

If I have a class with a template:

template<typename T>
class foo{
    T m_a;

    foo(T a){
        m_a = a;
    };

    ~foo(){

    };
};

有没有办法存储它的多个变体?

Is there a way to store multiple variation of it ?

例如一个可以存储指向foo<的指针的向量.int > 和 foo<字符串>同时?

For example a vector that can store a pointer to foo< int > and foo< string > at the same time ?

编辑更多信息

我想隐藏这个的实现:

EventListener<string> ev1;
EventListener<int, int> ev2;
EventListener<int, string, double> ev3;

ev1(&Events::nameChange, &nameChangeCallback);
ev2(&Events::healthChange, &healthChangeCallback);
ev3(&Events::newUser, &newUserCallback);

ev1.processEvents();
ev2.processEvents();
ev3.processEvents();

进入这个:

EventManager em;
em.listen(&Events::nameChange, &nameChangeCallback);
em.listen(&Events::healthChange, &healthChangeCallback);
em.listen(&Events::newUser, &newUserCallback);
em.processEvents();

EventManager 需要创建 EventListener 并将其存储到一个向量中，以便能够记住它们并在析构函数中删除它们.

EventManager needs to create and store EventListeners into a vector to be able to remember them and delete them in the destructor.

这就是我卡住的地方.

推荐答案

如果你想要例如std::vector<foo<T>*>，那么你需要使用一个非模板化的基类.它需要使用动态调度，所以所有的公共接口都应该声明为virtual.

If you want e.g. std::vector<foo<T>*>, then you need to use a non-templated base class. It will need to use dynamic dispatch, so all of the public interface should be declared virtual.

struct foo_base {
    virtual ~foo_base() {}
    virtual void something() = 0;
};

template <typename T>
struct foo : foo_base {
    // ...
    void something() { /* do something with T */ }
};

那么你的容器就是 std::vector.另一种可能更好的方法是使用 boost::variant.这限制了您可以存储的类型数量，但同时不需要基类和虚拟接口.

Then your container is std::vector<foo_base*>. Another, perhaps better, way, is to use boost::variant. This limits the number of types you can store, but at the same time doesn't require base class and virtual interface.

typedef boost::variant<foo<int>, foo<std::string>> foo_variants;
std::vector<foo_variants> v;

第三种方法是使用 boost::any，但这将需要 boost::any_cast 在任何地方使用它们，并且绝对允许将任何内容存储在向量中.

Third way is to use boost::any, but that will require boost::any_cast wherever you use them, and allow absolutely anything to be stored in the vector.

std::vector<boost::any> v;

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