Threading and Polymorphism





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-2















#include<iostream> 

#include <thread>

#include <algorithm>

#include <vector>

#include <functional>

using namespace std; 



class base 

{ 

public: 

    virtual void fun_1() { cout << "base-1n"; } 

    virtual void fun_2() { cout << "base-2n"; } 



}; 



class derived : public base 

{ 

public: 

    void fun_1() { cout << "derived-1n"; } 

    void fun_2() { cout << "derived-2n"; 

    } 

}; 





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;

}


I have a written a very simple threading and polymorphism example. All I wanted to do is to call a derived function from a different class which is containing that another class object. The program fails to compile with the message p does not name a type which I could not understand why.






c++







share|improve this question




















  • 5





    p = &obj1 doesn't make sense in the body of the class definition. It's a statement, and must be within some function, say me.

    – Igor Tandetnik
    Nov 22 '18 at 14:15






  • 3





    You can't have generic statements in the declaration section of a class, all statements must be inside functions. I also think you should read more about constructor initializer lists as a way to initialize members (like p).

    – Some programmer dude
    Nov 22 '18 at 14:15








  • 1





    You don't need p, you can pass &obj1 to bind.

    – molbdnilo
    Nov 22 '18 at 14:29











  • Just a suggestion: you don't need caller if all you want to do is explore polymorphism and threads. In main: derived obj1; base *p = &obj1; std::thread t(&base::fun_2, p); t.join();. The constructor for std::thread does just about everything that std::bind does.

    – Pete Becker
    Nov 22 '18 at 14:37











  • this question has nothing to do with threads

    – payo
    Nov 22 '18 at 16:24


















-2















#include<iostream> 

#include <thread>

#include <algorithm>

#include <vector>

#include <functional>

using namespace std; 



class base 

{ 

public: 

    virtual void fun_1() { cout << "base-1n"; } 

    virtual void fun_2() { cout << "base-2n"; } 



}; 



class derived : public base 

{ 

public: 

    void fun_1() { cout << "derived-1n"; } 

    void fun_2() { cout << "derived-2n"; 

    } 

}; 





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;

}


I have a written a very simple threading and polymorphism example. All I wanted to do is to call a derived function from a different class which is containing that another class object. The program fails to compile with the message p does not name a type which I could not understand why.






c++







share|improve this question




















  • 5





    p = &obj1 doesn't make sense in the body of the class definition. It's a statement, and must be within some function, say me.

    – Igor Tandetnik
    Nov 22 '18 at 14:15






  • 3





    You can't have generic statements in the declaration section of a class, all statements must be inside functions. I also think you should read more about constructor initializer lists as a way to initialize members (like p).

    – Some programmer dude
    Nov 22 '18 at 14:15








  • 1





    You don't need p, you can pass &obj1 to bind.

    – molbdnilo
    Nov 22 '18 at 14:29











  • Just a suggestion: you don't need caller if all you want to do is explore polymorphism and threads. In main: derived obj1; base *p = &obj1; std::thread t(&base::fun_2, p); t.join();. The constructor for std::thread does just about everything that std::bind does.

    – Pete Becker
    Nov 22 '18 at 14:37











  • this question has nothing to do with threads

    – payo
    Nov 22 '18 at 16:24














-2












-2








-2








#include<iostream> 

#include <thread>

#include <algorithm>

#include <vector>

#include <functional>

using namespace std; 



class base 

{ 

public: 

    virtual void fun_1() { cout << "base-1n"; } 

    virtual void fun_2() { cout << "base-2n"; } 



}; 



class derived : public base 

{ 

public: 

    void fun_1() { cout << "derived-1n"; } 

    void fun_2() { cout << "derived-2n"; 

    } 

}; 





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;

}


I have a written a very simple threading and polymorphism example. All I wanted to do is to call a derived function from a different class which is containing that another class object. The program fails to compile with the message p does not name a type which I could not understand why.






c++







share|improve this question
















#include<iostream> 

#include <thread>

#include <algorithm>

#include <vector>

#include <functional>

using namespace std; 



class base 

{ 

public: 

    virtual void fun_1() { cout << "base-1n"; } 

    virtual void fun_2() { cout << "base-2n"; } 



}; 



class derived : public base 

{ 

public: 

    void fun_1() { cout << "derived-1n"; } 

    void fun_2() { cout << "derived-2n"; 

    } 

}; 





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;

}


I have a written a very simple threading and polymorphism example. All I wanted to do is to call a derived function from a different class which is containing that another class object. The program fails to compile with the message p does not name a type which I could not understand why.






c++




c++






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 22 '18 at 16:24









payo

3,67911529




3,67911529










asked Nov 22 '18 at 14:13









Roshan MehtaRoshan Mehta

86711032




86711032








  • 5





    p = &obj1 doesn't make sense in the body of the class definition. It's a statement, and must be within some function, say me.

    – Igor Tandetnik
    Nov 22 '18 at 14:15






  • 3





    You can't have generic statements in the declaration section of a class, all statements must be inside functions. I also think you should read more about constructor initializer lists as a way to initialize members (like p).

    – Some programmer dude
    Nov 22 '18 at 14:15








  • 1





    You don't need p, you can pass &obj1 to bind.

    – molbdnilo
    Nov 22 '18 at 14:29











  • Just a suggestion: you don't need caller if all you want to do is explore polymorphism and threads. In main: derived obj1; base *p = &obj1; std::thread t(&base::fun_2, p); t.join();. The constructor for std::thread does just about everything that std::bind does.

    – Pete Becker
    Nov 22 '18 at 14:37











  • this question has nothing to do with threads

    – payo
    Nov 22 '18 at 16:24














  • 5





    p = &obj1 doesn't make sense in the body of the class definition. It's a statement, and must be within some function, say me.

    – Igor Tandetnik
    Nov 22 '18 at 14:15






  • 3





    You can't have generic statements in the declaration section of a class, all statements must be inside functions. I also think you should read more about constructor initializer lists as a way to initialize members (like p).

    – Some programmer dude
    Nov 22 '18 at 14:15








  • 1





    You don't need p, you can pass &obj1 to bind.

    – molbdnilo
    Nov 22 '18 at 14:29











  • Just a suggestion: you don't need caller if all you want to do is explore polymorphism and threads. In main: derived obj1; base *p = &obj1; std::thread t(&base::fun_2, p); t.join();. The constructor for std::thread does just about everything that std::bind does.

    – Pete Becker
    Nov 22 '18 at 14:37











  • this question has nothing to do with threads

    – payo
    Nov 22 '18 at 16:24








5




5





p = &obj1 doesn't make sense in the body of the class definition. It's a statement, and must be within some function, say me.

– Igor Tandetnik
Nov 22 '18 at 14:15





p = &obj1 doesn't make sense in the body of the class definition. It's a statement, and must be within some function, say me.

– Igor Tandetnik
Nov 22 '18 at 14:15




3




3





You can't have generic statements in the declaration section of a class, all statements must be inside functions. I also think you should read more about constructor initializer lists as a way to initialize members (like p).

– Some programmer dude
Nov 22 '18 at 14:15







You can't have generic statements in the declaration section of a class, all statements must be inside functions. I also think you should read more about constructor initializer lists as a way to initialize members (like p).

– Some programmer dude
Nov 22 '18 at 14:15






1




1





You don't need p, you can pass &obj1 to bind.

– molbdnilo
Nov 22 '18 at 14:29





You don't need p, you can pass &obj1 to bind.

– molbdnilo
Nov 22 '18 at 14:29













Just a suggestion: you don't need caller if all you want to do is explore polymorphism and threads. In main: derived obj1; base *p = &obj1; std::thread t(&base::fun_2, p); t.join();. The constructor for std::thread does just about everything that std::bind does.

– Pete Becker
Nov 22 '18 at 14:37





Just a suggestion: you don't need caller if all you want to do is explore polymorphism and threads. In main: derived obj1; base *p = &obj1; std::thread t(&base::fun_2, p); t.join();. The constructor for std::thread does just about everything that std::bind does.

– Pete Becker
Nov 22 '18 at 14:37













this question has nothing to do with threads

– payo
Nov 22 '18 at 16:24





this question has nothing to do with threads

– payo
Nov 22 '18 at 16:24












1 Answer
1






active

oldest

votes


















1














Your error is in line:



p = &obj1;


It is better to write like this, it should help:



class caller

{

private:

    derived obj1;

    base *p = &obj1;

......

};


or initialize pointer in costructor:



class caller

{

private:

    derived obj1;

    base *p = nullptr;

    caller() : p(&obj1) {}

......

};





share|improve this answer


























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    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    1














    Your error is in line:



    p = &obj1;


    It is better to write like this, it should help:



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


    or initialize pointer in costructor:



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





    share|improve this answer






























      1














      Your error is in line:



      p = &obj1;


      It is better to write like this, it should help:



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


      or initialize pointer in costructor:



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





      share|improve this answer




























        1












        1








        1







        Your error is in line:



        p = &obj1;


        It is better to write like this, it should help:



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


        or initialize pointer in costructor:



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





        share|improve this answer















        Your error is in line:



        p = &obj1;


        It is better to write like this, it should help:



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


        or initialize pointer in costructor:



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






        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Nov 22 '18 at 14:30

























        answered Nov 22 '18 at 14:19









        snake_stylesnake_style

        1,156511




        1,156511
































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