成员参数的c++运行时实例化

Question

正如标题所说，我想启动一个 Store 对象，其类型仅在运行时确定。我最初选择了一个虚拟类、2 个派生类，但很快就遇到了对模板的需求。

O 类有一个指向这些 Store 对象的接口(interface) BaseStore 的指针。此外，由于我还需要为派生类 Store1 和 Store2 调用正确的函数，因此我在接口(interface)的模板函数中使用了动态转换。

由于本人是c++新手，不知道这样的设计有没有缺陷，有没有可以改进的地方。感谢您的专业知识!

#include <iostream>
using namespace std;

struct BaseStore {
   virtual ~BaseStore() {}
   template<typename S> void test() const;
};

struct Store1 : public BaseStore {
   Store1(int j) { this->i = j; }
   void test() const { cout << i << endl; }
 private:
   int i = 1;
};

struct Store2 : public BaseStore {
   Store2(string s) { this->i = s; }
   void test() const { cout << i << endl; }
 private:
   string i = "2";
};

template<typename S> void BaseStore::test() const
{
dynamic_cast<const S&>(*this).test();
}

class O {
  public:
    O(int i) {
      this->type = i;
      switch (this->type) {
       case 1: basestore = new Store1(42); break;
       case 2: basestore = new Store2("lol"); break;
      }
    }
    ~O() { delete basestore; }
  void test() const {
    switch (this->type) {
     case 1: basestore->test<Store1>(); break; 
     case 2: basestore->test<Store2>(); break;
    }
  }
 private:
   int type;
   BaseStore* basestore;
 };

Answer 1

我相信虚函数和工厂模式会有所帮助，如:

struct BaseStore
{
    virtual ~BaseStore() = default;
    virtual void test() const = 0;

    BaseStore() = default;
    BaseStore(BaseStore const&) = delete;
    BaseStore(BaseStore&&) = delete;
    BaseStore& operator=(BaseStore&&) = delete;
    BaseStore& operator=(BaseStore const&) = delete;

};

struct Store1 : public BaseStore {
   Store1(int j) : i(j) {}
   void test() const override { std::cout << i << std::endl; }
 private:
   int i = 1;
};

struct Store2 : public BaseStore {
   Store2(std::string s) : i(std::move(s)) {}
   void test() const override { std::cout << i << std::endl; }
 private:
   std::string i = "2";
};

class O {
public:
    O(int i) : type(i), basestore(StoreFactory(i)) {}
    void test() const { basestore->test(); }

private:

    static std::unique_ptr<BaseStore> StoreFactory(int i)
    {
        switch (i)
        {
        case 1: return std::unique_ptr<Store1>(new Store1(42));
        case 2: return std::unique_ptr<Store2>(new Store2("lol"));
        default: throw std::runtime_error("Don't know what kind of Store you want");
        }
    }

   int type;
   std::unique_ptr<BaseStore> basestore;
 };