[c++]dynamic_pointer_cast用于shared_ptr之间类型的转换,基类需要有虚函数
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//编译错误
#include <memory>
#include <iostream>
class base
public:
base()std::cout << "base" << std::endl;
~base()std::cout << "~base" << std::endl;
void print()std::cout << "base::print" << std::endl;
;
class derived:public base
public:
derived()std::cout << "derived" << std::endl;
~derived()std::cout << "~derived" << std::endl;
void print()std::cout << "derived::print" << std::endl;
;
int main()
std::shared_ptr<base> b_ptr = std::make_shared<derived>();
b_ptr->print();
auto d_ptr = std::dynamic_pointer_cast<derived>(b_ptr);
d_ptr->print();
return 0;
//变异运行正常
#include <memory>
#include <iostream>
class base
public:
base()std::cout << "base" << std::endl;
virtual ~base()std::cout << "~base" << std::endl;
void print()std::cout << "base::print" << std::endl;
;
class derived:public base
public:
derived()std::cout << "derived" << std::endl;
~derived()std::cout << "~derived" << std::endl;
void print()std::cout << "derived::print" << std::endl;
;
int main()
std::shared_ptr<base> b_ptr = std::make_shared<derived>();
b_ptr->print();
auto d_ptr = std::dynamic_pointer_cast<derived>(b_ptr);
d_ptr->print();
return 0;
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