Inheritance basics

Learn to inherit from a base class with the : operator.

Inheritance basics

In C++, inheritance lets a class take over the members of another class. The class that inherits is the derived class; the class inherited from is the base class. It is written with a colon and an access modifier.

Example: class Dog : public Animal { };. Here Dog inherits from Animal. Dog has all public members of Animal and can add its own. This reduces code duplication: shared behavior is written once in Animal and inherited by classes like Dog and Cat.

Inheriting members

The derived class inherits the public and protected members of the base class. private members are not inherited; only the base class itself can access them. The derived class can reach them indirectly through the base class's member functions.

Example: if Animal has protected: std::string name;, Dog can use it directly: name = "Rex";. But if it were private, Dog could not access it; Animal would need a getName() function. That is why protected is common for inheritance.

Exercise Derive Dog from Animal

Define an Animal class: under public: the member function void breathe() { std::cout << "Breath"; }. Then derive Dog with class Dog : public Animal { };. In main create Dog d; and call d.breathe().

Show example solution

#include <iostream>

class Animal {
public:
    void breathe() {
        std::cout << "Breath";
    }
};

class Dog : public Animal {
};

int main() {
    Dog d;
    d.breathe();
    return 0;
}

Test yourself

In class Dog : public Animal { };, what is Animal?
```
class Dog : public Animal { };
```
- A member variable of Dog
- A constructor of Dog
- The base class of Dog
- A friend class of Dog
Show answer

The base class of Dog — Animal is the base class that Dog inherits from.

Complete the inheritance syntax

class Dog ____ public Animal { };

Show answer

class Dog : public Animal { };

Match each term to its role

Animal

Base class
Dog

Derived class
public

Inheritance access type
:

Inheritance relation

Next lesson: virtual

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