Operator Overloading

Via operator overloading we can use operators among class instances.

The key for operator predefining is to create function named specifically via the keyword operator.

For example a + operator can be predefined via a function named operator+

> operator can be predefined via a function named operator> and so on.

Arithmetic Operator Example

#include <iostream> using namespace std; class Car { private: string model; double price; public: Car(string modelValue, double priceValue) { model = modelValue; price = priceValue; } // Operator "+" predefining: double operator+(Car rightCar) { // price of left side object // + price of right side object: return price + rightCar.price; } }; void main() { Car toyotaCar("Toyota Corolla", 35000); Car renaultCar("Renault Clio", 18000); cout << "Price of both cars:" << endl; cout << toyotaCar + renaultCar << " $"; }

Output:

Price of both cars: 53000 $

Line 32 sums two class objects. This executes the code of the predefining operator function (lines 18 - 23).

Comparision Operator Example

#include <iostream> #include <string> using namespace std; class Car { private: string model; double price; public: Car(string modelValue, double priceValue) { model = modelValue; price = priceValue; } // Predefining operator "==": bool operator==(Car rightCar) { // price of left side object // == price of right side object return price == rightCar.price; } }; void main() { Car toyotaCar("Toyota Corolla", 35000); Car peugeotCar("Peugeot 308", 35000); Car renaultCar("Renault Clio", 18000); if (toyotaCar == peugeotCar) { cout << "Toyota Car = Peugeot Car"; } if (peugeotCar == renaultCar) { cout << "Peugeot Car = Renault Car"; } if (renaultCar == toyotaCar) { cout << "Renault Car = Toyota Car"; } }

Output:

Toyota Car = Peugeot Car

Lines 33, 38 and 43 compare objects via the operator ==. To compare them the code from the operator predefined function is used (lines 19 - 24).

Assignment Operator Example

#include <iostream> #include <string> using namespace std; class Car { private: string model; double price; public: Car(string modelValue, double priceValue) { model = modelValue; price = priceValue; } // Predefining operator "=": void operator=(Car rightCar) { model = rightCar.model; price = rightCar.price; } void printData() { cout << "Model: " << model << endl; cout << "Price: " << price << " $" << endl;; } }; void main() { Car carObj1("Toyota Corolla", 35000); Car carObj2("Ford Fiesta", 25000); cout << "Before Assignment: " << endl; carObj1.printData(); cout << "- - - - -" << endl; carObj2.printData(); carObj1 = carObj2; cout << endl << endl; cout << "After Assignment: " << endl; carObj1.printData(); cout << "- - - - -" << endl; carObj2.printData(); }

Output:

Before Assignment: Model: Toyota Corolla Price: 35000 $ - - - - - Model: Ford Fiesta Price: 25000 $ After Assignment: Model: Ford Fiesta Price: 25000 $ - - - - - Model: Ford Fiesta Price: 25000 $