为什么我只能在子类（派生类）的方法中访问 class 的受保护成员？

Question

#include <iostream>
using namespace std;

class parent
{
protected:
    int main = 0;
};

class subclass : public parent
{
    cout << main;  //error
    void function() //ok
    {
        cout << main;
    }
};

I have this code right here where i tried to cout main outside of the function and one inside the function. However i can only access main inside the function but not outside of the function. But why tho?

Answer 1

The problem is that the statement cout << main; cannot appear "directly" inside the member-specification of a class. It should instead be inside a member function.

From class members :

member-specification:

• member-declaration member-specificationopt

• access-specifier: member-specificationopt

As per the above quoted grammer rules, cout << main is not allowed to appear directly inside the member specification of a class.