The Four Pillars of OOP

Core idea

The classic four pillars are encapsulation, abstraction, inheritance, and polymorphism. They describe common ways object-oriented code stays manageable.

The pillars

• Encapsulation keeps related data and behavior together.
• Abstraction hides unnecessary details.
• Inheritance allows one class to build on another.
• Polymorphism lets different objects respond to the same message in different ways.

class Animal {
public:
  virtual void speak() const {
    std::cout << "Some sound\n";
  }
};

What to remember

These ideas are helpful, but not every design needs all four. Use them when they make your code easier to reason about.