Creating object with constant parameters from stream

Question

let us assume I have a class with

#include 
using namespace std;

class Test{
    public:
        friend istream& operator >> (istr         


        

Answer 1

Define a Dummy class:

class Dummy {
public:
    Dummy() { value = 0; }
    friend istream& operator >> (istream& input, const Dummy& dummy){
        input >> dummy.value;
        return input;
    }
    friend ostream& operator << (ostream& output, const Dummy& dummy){
        output << dummy.value << endl;
        return output;
    }
    int getValue() const { return value; }
private:
    mutable int value;
};

And use it in Test:

class Test {
public:
    Test() { cin >> dummy; }
private:
    const Dummy dummy;
};

It works as expected.