C++ Classes vs Structs Notes

By The Cherno | Full Playlist 🔗

1. Key Difference: Default Visibility

📌 Only Technical Difference:

• class: Members are private by default.
• struct: Members are public by default.

Example:

// Class (private by default)  
class Player {  
    int x, y; // Private  
public:  
    void move() { /* ... */ } // Public  
};  

// Struct (public by default)  
struct Vec2 {  
    float x, y; // Public  
    void add(const Vec2& other) { /* ... */ } // Public  
};  

Video Reference 🎥

2. When to Use Struct vs Class

Struct Usage:

• Plain Old Data (POD): Group related variables (e.g., Vec2, Color).
• No complex functionality: Avoid inheritance; focus on data storage.

  struct Vec2 {  
    float x, y;  
    void add(const Vec2& other) {  
        x += other.x;  
        y += other.y;  
    }  
  };  
  

Class Usage:

• Complex objects: Combine data + methods (e.g., Player, GameWorld).
• Inheritance: Use for class hierarchies.

  class Player {  
  private:  
    int health;  
  public:  
    void attack() { /* ... */ }  
  };  
  

  Video Reference 🎥

3. Backward Compatibility with C

• Structs exist in C: C++ retains struct for compatibility.
• C code: Replace struct with class + public to compile in C++.

Example:

// C code  
struct Point {  
    int x, y; // Public in C  
};  

// Equivalent C++ code  
class Point {  
public:  
    int x, y;  
};  

Video Reference 🎥

4. Best Practices

1. Use struct for data containers:

   struct Transform {  
       float position[3];  
       float rotation[3];  
   };  
   

2. Use class for complex logic:

   class Enemy : public Character {  
   private:  
       int damage;  
   public:  
       void attack() { /* ... */ }  
   };  
   

3. Avoid mixing inheritance:
   • Compilers warn if a struct inherits from a class.

Video Reference 🎥

Cheat Sheet

| Feature | Class | Struct |
|—————————|————————————|————————————-|
| Default Visibility | private | public |
| Typical Use Case | Complex objects, inheritance | Data grouping (POD) |
| Inheritance | Preferred for hierarchies | Avoid |

💡 Pro Tip: Use struct for simple data bags and class for objects with behavior. Keep code readable!