c++ - std::shared_ptr 和继承

Question

我在继承类的 shared_ptr 之间的自动类型转换方面遇到了一些问题。

我的类结构如下，一个基类Base和两个派生类Derived1和Derived2。

// Base class
class Base {
protected:
  ...
  ...
public:
  Base() = default;
  virtual ~Base() = default;
  virtual void run() = 0;
  ...
  ...
};

// Derived class
class Derived1: Base {
protected:
  ...
  ...
public:
  Derived1() = default;
  virtual ~Derived1() = default;
  void run() {...}
  ...
  ...
};

// Derived class
class Derived2: Base {
protected:
  ...
  ...
public:
  Derived2() = default;
  virtual ~Derived2() = default;
  void run() {...}
  ...
  ...
};

我有一个函数doSomething()

void doSomething(std::shared_ptr<Base> ptr) {
  ptr->run();
  ...
}

我像这样用派生类调用函数-

doSomething(make_shared<Derived1>())
doSomething(make_shared<Derived2>())

但我收到一条错误消息 -

no viable conversion from 'shared_ptr<class Derived1>' to 'shared_ptr<class Base>'
no viable conversion from 'shared_ptr<class Derived1>' to 'shared_ptr<class Base>'

我做错了什么？仅将 static_pointer_cast 用于 Base 类型是否安全？喜欢-

doSomething(static_pointer_cast<Base>(make_sahred<Derived2>()))

解决方案我的错...问题是我私下继承了基类。

Answer 1

据我所知，您提供的代码编译良好:http://ideone.com/06RB2W

#include <memory>

class Base {
    public:
        Base() = default;
        virtual ~Base() = default;
        virtual void run() = 0;
};

class Derived1: public Base {
    public:
        Derived1() = default;
        virtual ~Derived1() = default;
        void run() {}
};

class Derived2: public Base {
    public:
        Derived2() = default;
        virtual ~Derived2() = default;
        void run() {}
};

void doSomething(std::shared_ptr<Base> ptr) {
    ptr->run();
}

int main() {
    doSomething(std::make_shared<Derived1>());
    doSomething(std::make_shared<Derived2>());
}