How to declare and call virtual functions in C++?
Apr 12, 2024 pm 04:03 PM
Virtual function is a polymorphism mechanism that allows a derived class to override the member function of its base class: Declaration: Add the keyword virtual before the function name. Call: Using a base class pointer or reference, the compiler will dynamically bind to the appropriate implementation of the derived class. Practical case: By defining the base class Shape and its derived classes Rectangle and Circle, the application of virtual functions in polymorphism is demonstrated to calculate area and draw shapes.
Virtual function in C
Virtual function is a polymorphism mechanism that allows a derived class to override the properties of its base class Member functions. This enables programmers to define common behavior in a base class while still allowing derived classes to provide its instance-specific implementation of that behavior.
Declaring virtual functions
To declare a virtual function, place the keyword virtual at the beginning of the function name. For example:
class Base {
public:
virtual void print() const;
};Call virtual function
Call virtual function, use base class pointer or reference. The compiler will dynamically bind to the appropriate implementation of the derived class. For example:
void doSomething(Base* base) {
base->print();
}Practical case
The following is an example of using virtual functions:
#include <iostream>
class Shape {
public:
virtual double area() const = 0;
virtual void draw() const = 0;
};
class Rectangle : public Shape {
public:
Rectangle(double width, double height) : width_(width), height_(height) {}
double area() const override { return width_ * height_; }
void draw() const override { std::cout << "Drawing rectangle" << std::endl; }
private:
double width_;
double height_;
};
class Circle : public Shape {
public:
Circle(double radius) : radius_(radius) {}
double area() const override { return 3.14 * radius_ * radius_; }
void draw() const override { std::cout << "Drawing circle" << std::endl; }
private:
double radius_;
};
int main() {
Shape* rectangle = new Rectangle(5, 10);
Shape* circle = new Circle(5);
std::cout << rectangle->area() << std::endl; // Output: 50
std::cout << circle->area() << std::endl; // Output: 78.5
rectangle->draw(); // Output: Drawing rectangle
circle->draw(); // Output: Drawing circle
return 0;
}The above is the detailed content of How to declare and call virtual functions in C++?. For more information, please follow other related articles on the PHP Chinese website!
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