Detailed explanation of C++ function inheritance: How to understand the "is-a" and "has-a" relationship in inheritance?

C Detailed explanation of function inheritance: Master the relationship between "is-a" and "has-a"

What is function inheritance?

Function inheritance is a technique in C that associates methods defined in a derived class with methods defined in a base class. It allows derived classes to access and override methods of the base class, thereby extending the functionality of the base class.

"is-a" and "has-a" relationship

In function inheritance, "is-a" relationship refers to the derived class It is a subtype of the base class, that is, the derived class "inherits" the characteristics and behavior of the base class. "has-a" relationship means that the derived class contains a reference or pointer to the base class object, that is, the derived class "owns" the base class object.

Grammar

The following is the syntax for how to implement function inheritance:

class DerivedClass : public BaseClass {
public:
  // 派生类中定义的方法（可能会重写基类方法）
};

Practical case

Let We understand function inheritance through a simple example:

Base class Shape

class Shape {
public:
  virtual void draw() {
    // 基类绘图行为
  }
};

Derived class Rectangle

Derived class Rectangle "is-a" Shape, that is, Rectangle is a type of Shape. It inherits the draw() method of Shape and overrides it to provide specific drawing behavior for rectangles:

class Rectangle : public Shape {
public:
  virtual void draw() override {
    // 派生类绘图行为（绘制矩形）
  }
};

Usage example

Now, we can use the Rectangle class to create the object and call the draw() method:

Rectangle rectangle;
rectangle.draw(); // 调用派生类中重写的绘图行为

Conclusion

By understanding the "is-a" and "has-a" relationships, you can use it efficiently Function inheritance to extend the functionality of C classes and create more organized and maintainable code.

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