slice.cpp

#include <iostream>
#include <string>

class Employee
{
    std::string m_name;

protected:
    virtual void print(std::ostream& os) const { os << "Employee: " << get_name() << std::endl; }

public:
    Employee(const std::string& name) : m_name(name) {}
    const std::string& get_name() const { return m_name; }
    friend std::ostream& operator<<(std::ostream& os, const Employee& e)
    {
        e.print(os);
        return os;
    }
};

class Manager : public Employee
{
    Employee m_assistant;

protected:
    void print(std::ostream& os) const override
    {
        os << "Manager: " << get_name() << std::endl;
        os << "Assistant: " << std::endl << "\t" << get_assistant() << std::endl;
    }

public:
    Manager(const std::string& name, const Employee& assistant)
        : Employee(name), m_assistant(assistant)
    {}
    const Employee& get_assistant() const { return m_assistant; }
};

/// OOP51-CPP. Do not slice derived objects
void bad(Employee e) { std::cout << e; } // diagnostic required

void good(const Employee& e) { std::cout << e; }

int main()
{
    Employee coder("Joe Smith");
    Employee typist("Bill Jones");
    Manager designer("Jane Doe", typist);

    bad(coder);
    bad(typist);
    bad(designer);

    good(designer);
}