Question

#include <iostream>
#include <cstring>
using namespace std;

class Obj;


class Test {
    friend class Obj;
public:
    Test()
    {

    }
    ~Test()
    {

    }
    void foo()
    {
        //print();
            //Obj::print();
            //Obj x;
            //x.print();
    }
};

class Obj {
public:
    void print()
    {
        cout << "print here" << endl;
    }
};

int main()
{
    Test test;
    test.foo();
    return 0;
}

Quick question,how can I call print the correct way in Test::foo() ?

Answer 1

You need to define the member function after the definition of Obj:

class Test { 
public:
    void foo();
};

class Obj {
public:
    void print() { }
};

void Test::foo() { 
    Obj o;
    o.print();
}