Inheritance & Classes in C++

Question

I don't understand this

class Employee { 
       public:   
          Employee(string name, float payRate); 
          string getName();   
          float getPayRate(); 
          float pay(float hoursWorked); 
       protected:   
          string name;   
          float payRate; 
}; 
class Manager : public Employee { 
       public:   
          Manager(string theName, float thePayRate, bool isSalaried); 
          bool getSalaried() const; 
          float pay(float hoursWorked) const; 
       private:   
          bool salaried; 
};

Suppose the pay() method has been declared virtual in Employee. And, we add a printPay() method to the Employee class:

void Employee::printPay(float hoursWorked) const 
{  
    cout << "Pay: " << pay(hoursWorked) << endl; 
} 

which gets inherited in Manager without being overridden.

Which version of pay() will be called within printPay() for a Manager when mgr object calls printPay(). Explain your answer.

Manager mgr; 
mgr.printPay(40.0);

This is the answer provided:

The Manager version of pay() gets called inside of printPay() even though printPay() was only defined in Employee! Why? Remember that:

void Employee::printPay(float hoursWorked) const 
{   
    ... pay(hoursWorked) ... 
} 

is really shorthand for:

void Employee::printPay(float hoursWorked) const 
{   
    ... this->pay(hoursWorked) ... 
} 

What does that even mean? Why isn't the answer polymorphism.

Answer 1

The thing is that this type in your printPay function is not Employee , but const Employee . So your function Employee::pay(hoursWorked) does not match.

In clang++, the following error is issued:

28 : <source>:28:24: error: member function 'pay' not viable: 'this' 
argument has type 'const Employee', but function is not marked const
cout << "Pay: " << pay(hoursWorked) << endl; 
                   ^~~
11 : <source>:11:17: note: 'pay' declared here
      float pay(float hoursWorked);