Adding [Term Entry] C++ Inheritance: Multiple Inheritance

content/cpp/concepts/inheritance/terms/multiple-inheritance/multiple-inheritance.md

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+---
+Title: 'Multiple Inheritance'
+Description: 'Allows classes to inherit characteristics from more than one base class.'
+Subjects:
+  - 'Computer Science'
+  - 'Code Foundations'
+Tags:
+  - 'Abstraction'
+  - 'Classes'
+  - 'Objects'
+CatalogContent:
+  - 'learn-c-plus-plus'
+  - 'paths/computer-science'
+---
+
+**Multiple inheritance** is a type of [inheritance](https://www.codecademy.com/resources/docs/cpp/inheritance) where classes can inherit from more than one base class.
+
+## Syntax
+
+The syntax for multiple inheritance is similar to the syntax for single inheritance:
+```pseudo
+class DerivedClass : public BaseClass1, public BaseClass2 {
+    // Derived class members
+};
+```
+
+Classes can inherit from as many base classes as necessary, and, as with single inheritance, access modifiers can be used to modify access for inherited members.
+
+The ordering of base classes affects the order in which [constructors](https://www.codecademy.com/resources/docs/cpp/constructors) and [destructors](https://www.codecademy.com/resources/docs/cpp/destructors) are called:
+
+- Virtual base class constructors are called first (from left to right).
+- Direct base class constructors are then called (from left to right).
+- Destructors are called in reverse order of constructors.
+
+
+## Examples
+
+### Basic multiple inheritance
+
+```cpp
+class Bat { 
+  public: 
+    void fly();
+}; 
+
+class Man { 
+  public: 
+      void run();
+};
+
+class ManBat : public Man, public Bat { 
+  // run() and fly() are both available as they're inherited from Man and Bat 
+}; 
+```
+
+### Ambiguity errors
+
+With multiple inheritance, ambiguity errors can occur if two base classes have members with identical names. This happens because it is unclear which base class member should be referenced. The **scope resolution operator** (`::`) can resolve such conflicts.
+
+```cpp
+class Dancer { 
+  public: 
+    void jump();
+}; 
+
+class Frog { 
+  public: 
+      void jump();
+};
+
+class DancingFrog : public Dancer, public Frog { 
+  // jump() is inherited from Dancer and Frog
+}; 
+
+int main () {
+  DancingFrog df;
+  df.jump(); // This will cause an ambiguity error as it isn't clear which ancestor's jump() we mean
+  df.Dancer::jump(); // This won't cause an ambiguity error as the scope resolution operator explicitly references Dancer
+  return 0;
+}   
+```
+
+### The Diamond Problem
+
+Ambiguity errors can also occur if multiple base classes inherit from a common ancestor. This is known as the **Diamond Problem**.
+
+```cpp
+class Vehicle {
+  public:
+    void weight();
+};
+
+class Car : public Vehicle {
+  // Inherits weight() from Vehicle
+  public:
+      void drive();
+};
+
+class Plane : public Vehicle { 
+  // Inherits weight() from Vehicle
+  public:
+      void fly();
+}; 
+
+class CarPlane : public Car, public Plane {
+  // Inherits drive() from Car and fly() from Plane
+  // Inherits weight() twice, once from Car and once from Plane, as each will have their own Vehicle object
+  public:
+      void switchMode();
+};
+
+int main () {
+  CarPlane cp;
+  cp.weight(); // Causes an ambiguity error as CarPlane as there are two Vehicle ancestor objects
+  return 0;
+}
+```
+
+### Resolving the Diamond Problem with Virtual Inheritance
+
+One way to fix the diamond problem is to use virtual inheritance in the intermediate classes.
+
+```cpp
+class Vehicle {
+  public:
+    void weight();
+};
+
+class Car : virtual Vehicle {
+  // Inherits weight() from Vehicle
+  public:
+      void drive();
+};
+
+class Plane : virtual Vehicle { 
+  // Inherits weight() from Vehicle
+  public:
+      void fly();
+}; 
+
+class CarPlane : public Car, public Plane {
+  // Inherits drive() from Car and fly() from Plane
+  // Inherits weight() once, as Car and Plane both reference the same Vehicle ancestor object
+  public:
+      void switchMode();
+};
+
+int main () {
+  CarPlane cp;
+  cp.weight(); // This won't cause an ambiguity error as there is only one Vehicle ancestor object
+  return 0;
+}
+```
+
+## Codebyte Example
+
+Here's an example demonstrating multiple inheritance using a workplace scenario:
+
+```codebyte/cpp
+#include <iostream>
+using namespace std;
+
+// Base class 1
+class Employee {
+public:
+    void work() {
+        cout << "Employee is working on tasks.\n";
+    }
+};
+
+// Base class 2
+class Skill {
+public:
+    void coding() {
+        cout << "Employee is coding in C++.\n";
+    }
+};
+
+// Derived class inheriting from both Employee and Skill
+class SoftwareEngineer : public Employee, public Skill {
+public:
+    void debug() {
+        cout << "Software Engineer is debugging the code.\n";
+    }
+};
+
+int main() {
+    SoftwareEngineer dev;
+    dev.work();   // Inherited from Employee
+    dev.coding(); // Inherited from Skill
+    dev.debug();  // Defined in SoftwareEngineer
+
+    return 0;
+}
+```