How to deal with the trade-off between inheritance and polymorphism in C++ class design?

Both inheritance and polymorphism can achieve code reuse, but there are differences in trade-offs: Inheritance: Advantages: Promotes code reuse, implements "is-a" relationships Disadvantages: Tight coupling, fragile base class issues Polymorphism: Advantages : Promote loose coupling and improve code flexibility Disadvantages: Overhead, complexity In actual combat scenarios, inheritance can be used to establish the "is-a" relationship between base classes and derived classes; polymorphism can be used to implement different types of objects in the interface to unify way to respond to method calls.

C++ Class Design: Inheritance vs. Polymorphism Tradeoffs

Inheritance and Polymorphism in C++ Class Design are two basic concepts. While both allow code reuse, they have different tradeoffs.

Inheritance

Inheritance allows one class (derived class) to inherit properties and behavior from another class (base class).

• Advantages:

  • Promote code reuse
  • Achieve "is-a" relationship

• Disadvantages:

  • Tight coupling: Derived class depends on base class
  • Fragile base class problem: In base class Changes may affect derived classes

Polymorphism

Polymorphism allows an object to respond to different methods in a uniform way calls, regardless of their type.

• Advantages:

  • Promote loose coupling: objects communicate through interfaces rather than concrete types
  • Improve code Flexibility: Objects can be added and modified easily Additional memory and performance overhead
  Complexity: Implementing polymorphism requires careful interface design

• Practical case
  Suppose you need to design a program that manages various shapes such as triangles, squares, and circles.
  • Using inheritance, you create a base class
  Shape
that contains the common properties and methods of a shape. You can then create derived classes such as

Triangle

, Square, and

Circle

, which inherit from

Shape

and implement their own specific behavior. <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:cpp;toolbar:false;'>class Shape { public: virtual double area() const = 0; // 纯虚函数，必须在派生类中实现 }; class Triangle : public Shape { public: double area() const override { return 0.5 * base * height; } double base, height; }; class Square : public Shape { public: double area() const override { return side * side; } double side; }; class Circle : public Shape { public: double area() const override { return PI * radius * radius; } double radius; };</pre><div class="contentsignin">Copy after login</div></div>Using polymorphism, you can create a Shape interface that contains common methods for shapes. You can then create the Triangle, Square, and Circle classes that implement the interface.

class Shape {
public:
    virtual double area() const = 0;
};

class Triangle : public Shape {
public:
    double area() const override { return 0.5 * base * height; }
    double base, height;
};

class Square : public Shape {
public:
    double area() const override { return side * side; }
    double side;
};

class Circle : public Shape {
public:
    double area() const override { return PI * radius * radius; }
    double radius;
};

int main() {
    vector<Shape*> shapes;
    shapes.push_back(new Triangle());
    shapes.push_back(new Square());
    shapes.push_back(new Circle());

    for (Shape* shape : shapes) {
        cout << "Area: " << shape->area() << endl;
    }

    return 0;
}

Weighing considerationsWhen choosing inheritance versus polymorphism, you should consider the following factors:Relationship type :

If the subclass has an "is-a" relationship (i.e. a triangle is a shape), inheritance may be a better choice.

Coupling:

If you need to maintain loose coupling, polymorphism is a better choice.

Flexibility:
• Polymorphism provides greater flexibility if objects need to be modified frequently.
The best practice to make trade-offs is to use composition to take advantage of inheritance and polymorphism. For example, you can use inheritance to establish common relationships in a shape's base class, while using polymorphism to implement specific behaviors.

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