How to get a user's input into a class's member variable and dereference it-CodePudding

class cookie{
public:
    cookie() = default;
    int*p_member{};
    int case{};
private:
};

#include <iostream>
using namespace std;
int main(){
    cookie cold;
    cout << "Type what you want into the cookie p_member variable " << endl;
    std::cin >> cold.*p_member; // this doesn't work 
}

I wanna know how to get access to the classes pointer variable put data inside it and then derefrence it.

CodePudding user response：

First things first, make sure that you're not dereferencing a null or uninitialized pointer. Otherwise you'll have undefined behavior.

it's about a member that is a pointer.I would like to assign a value to the member, and then dereference the member so i could print it out.

You can use a pointer to member syntax for this task as shown below:

class cookie{
public:
    
    int var;
    int cookie::*p_member=&cookie::var; //p_member can point to an int data member of an cookie object 
    
};

int main(){
    cookie cold{};
    
    cout << "Type what you want into the cookie p_member variable " << endl;
    std::cin >> cold.*cold.p_member;  //take input from user directly into var using member pointer syntax
    
    std::cout << "var: " << cold.var << std::endl; //print var to confirm that it is correctly set
}

Working demo