Question

#include<iostream> 
#include <thread>
#include <algorithm>
#include <vector>
#include <functional>
using namespace std; 

class base 
{ 
public: 
    virtual void fun_1() { cout << "base-1\n"; } 
    virtual void fun_2() { cout << "base-2\n"; } 

}; 

class derived : public base 
{ 
public: 
    void fun_1() { cout << "derived-1\n"; } 
    void fun_2() { cout << "derived-2\n"; 
    } 
}; 


class caller
{
    private:
        base *p; 
        derived obj1; 
        p = &obj1;
    public:
        void me()
        {
                std::thread t(std::bind(&base::fun_2, p), this);
                t.join();
        }
};

int main() 
{  
    caller c;    
    c.me();
    return 0;
}

我写了一个非常简单的线程和多态示例。我要做的就是从另一个包含另一个类对象的类中调用派生函数。该程序无法编译消息p does not name a type，但我不明白为什么。

Answer 1

您的错误所在：

p = &obj1;

最好这样写，应该有帮助：

class caller
{
private:
    derived obj1;
    base *p = &obj1;
......
};

或在构造函数中初始化指针：

class caller
{
private:
    derived obj1;
    base *p = nullptr;
    caller() : p(&obj1) {}
......
};

线程和多态

1 个答案: