[英]shared_ptr from abstract class
I have this mediator pattern: 我有这种中介模式:
File actor.hpp
文件
actor.hpp
#pragma once
#include <memory>
#include "mediator.hpp"
class actor : std::shared_from_this<actor>
{
public:
actor(std::shared_ptr<mediator> mediator) : mediator_(mediator)
{
}
virtual ~actor() = 0;
virtual void changed()
{
mediator_->actor_changed(std::make_shared<actor>(this));
}
private:
std::shared_ptr<mediator> mediator_;
};
File mediator.hpp
文件
mediator.hpp
#pragma once
#include <memory>
class actor;
class mediator : public std::shared_from_this<mediator>
{
public:
virtual ~mediator() = 0;
virtual void actor_changed(std::shared_ptr<actor> actor) = 0;
}
An implementation of an actor request_handler.hpp
actor
request_handler.hpp
的实现
#pragma once
#include "actor.hpp"
class request_handler : public actor
{
public:
request_handler(std::shared_ptr<mediator> mediator) : actor(mediator)
{
}
void handle_request()
{
changed();
}
};
But I get the error message 但是我收到错误消息
actor.hpp:16 error: invalid new-expression of abstract class type 'actor'
because I cannot instatiate an abstract class. 因为我不能实例化一个抽象类。 But what would be the correct way of doing this?
但是,这样做的正确方法是什么?
This code: 这段代码:
mediator_->actor_changed(std::make_shared<actor>(this));
is logically equal to: 在逻辑上等于:
auto ptr = std::shared_ptr<actor>( new actor( this ) );
mediator_->actor_changed(ptr);
and this is most probably not what you want, so you need to call shared_from_this() instead: 并且这很可能不是您想要的,因此您需要调用shared_from_this() :
mediator_->actor_changed( this->shared_from_this() );
and class you need to inherit from is called std::enable_shared_from_this not shared_from_this
你需要从被称为继承类的std :: enable_shared_from_this不
shared_from_this
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