How to use polymorphism to handle differences between different objects in C++?

Polymorphism is an object-oriented programming feature that allows objects to behave differently at runtime, even if they have the same parent class. In C++, polymorphism is achieved through virtual functions and inheritance: Define a base class and a derived class: the base class contains virtual functions, and the derived class inherits the base class and overrides the virtual functions. Use pointers or references: Save the address of the base class object through a pointer or reference, and access objects of different derived classes at runtime. Calling via virtual function: Calling a virtual function in the base class will call the overridden derived class function at runtime. Practical case: In the shape class hierarchy, the Circle and Rectangle classes inherit the Shape class and override the area(), perimeter() and draw() virtual functions, allowing these shapes to be used

Practical application of polymorphism in C++

What is polymorphism?

Polymorphism is a feature in object-oriented programming languages ​​that allows objects to behave differently at runtime, even if they have the same parent class. In C++, polymorphism is achieved through virtual functions and inheritance.

How to use polymorphism?

1. Define base and derived classes: Define a base class that contains virtual functions. Derived classes inherit the base class and override virtual functions to provide different implementations.
2. Use pointers or references: Save the address of the base class object through a pointer or reference. This allows access to objects of different derived classes at runtime.
3. Call via virtual function: Call a virtual function in the base class and it will call the overridden derived class function at runtime, depending on the actual object type.

Practical case: Shape class hierarchy

Base class Shape

class Shape {
public:
  virtual double area() = 0;
  virtual double perimeter() = 0;
  virtual void draw() = 0;
};

Derived class Circle and Rectangle

class Circle : public Shape {
public:
  ...  // 构造函数和数据成员
  virtual double area() override;
  virtual double perimeter() override;
  virtual void draw() override;
};

class Rectangle : public Shape {
public:
  ...  // 构造函数和数据成员
  virtual double area() override;
  virtual double perimeter() override;
  virtual void draw() override;
};

Calculate area and perimeter using polymorphism

vector<Shape*> shapes;
shapes.push_back(new Circle(...));
shapes.push_back(new Rectangle(...));

for (auto& shape : shapes) {
  cout << "面积: " << shape->area() << endl;
  cout << "周长: " << shape->perimeter() << endl;
  shape->draw();
}

Advantages:

• Simplify the code and keep the base class and derived class decoupled.
• Improve the scalability and maintainability of the code.
• Allows dynamic processing of different objects at runtime.

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