Inheritance

concept oop Inheritance allows a class (Child/Subclass) to derive attributes and behavior from another class (Parent/Superclass). It promotes code reuse.

• Relationship: “Is-A” (e.g., A Car is a Vehicle).
• Mechanism: The child gets all public and protected members of the parent.

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Examples: Game Entities

C++

Supports Multiple Inheritance (can inherit from many parents).

class Enemy {
public:
    void attack() { cout << "Attacking!"; }
};
 
// Orc inherits from Enemy
class Orc : public Enemy {
public:
    void grunt() { cout << "Zug zug"; }
};

Java

Supports Single Inheritance (one parent) via extends.

class Enemy {
    public void attack() { System.out.println("Attacking!"); }
}
 
class Orc extends Enemy {
    public void grunt() { System.out.println("Zug zug"); }
}

Rust (No Inheritance)

Rust does not support struct inheritance. Instead, it uses Composition (containing a struct) or Traits (sharing behavior).

struct Enemy {
    hp: i32,
}
 
struct Orc {
    base: Enemy, // Composition: Orc "has an" Enemy struct inside
    clan: String,
}

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The Diamond Problem

If Class D inherits from both B and C, and both B and C inherit from A… does D get two copies of A?

• C++: Yes, unless you use virtual inheritance.
• Java: Avoids this by banning Multiple Inheritance of State (Classes), but allows Multiple Inheritance of Types (Interfaces).
• Rust: Avoids this entirely by not having inheritance.

Composition over Inheritance

Modern software engineering prefers Composition.

• Inheritance: You are locked into the parent’s structure. Fragile Base Class problem.
• Composition: You build complex objects by assembling smaller, independent components. (Lego blocks).

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