What are the design principles of C++ classes?

Class design principles are crucial in C++, and the following 5 principles help create effective and maintainable classes: Single responsibility principle: Each class is responsible for only one task. Open-Closed Principle: Classes can be extended without modification. Dependency Inversion Principle: Modules depend on abstract interfaces rather than concrete implementations. Interface isolation principle: Interfaces should be as small and targeted as possible. Liskov substitution principle: subclasses can seamlessly replace parent classes.

C++ Class Design Principles

Class design in C++ is crucial as it helps to create transparent, maintainable and scalable code. Following a few key design principles can greatly improve the effectiveness of your class design.

1. Single Responsibility Principle

Each class should be responsible for only one clearly defined task or responsibility. This makes classes easy to understand, test, and maintain.

2. Opening and closing principle

The class should be open for extension and not closed for modification. This means you can add new functionality or behavior to a class without modifying existing code.

3. Dependency inversion principle

Modules should not be directly dependent on each other. Instead, they should rely on abstract interfaces. This allows you to easily replace a module without modifying other modules that depend on it.

4. Interface isolation principle

Interfaces (abstract classes or pure virtual functions) should be as small and targeted as possible. This helps avoid unnecessary coupling and forced dependencies.

5. Liskov Substitution Principle

A subclass must be able to seamlessly replace its parent class. This means that subclasses can extend the behavior of the parent class without breaking existing client code.

Practical Case

Consider a class that manages employee information:

class Employee {
public:
    string name;
    int age;
    double salary;
};

This class violates the single responsibility principle because it handles both employee information and Calculate salary. A better design would be to move the salary calculation into a separate class:

class Employee {
public:
    string name;
    int age;
};

class SalaryCalculator {
public:
    virtual double calculateSalary(const Employee& employee) const = 0;
};

Now, SalaryCalculator is responsible for calculating salary so that Employee can focus on employee information . This follows the dependency inversion principle since Employee depends on the SalaryCalculator interface rather than any concrete implementation.

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