fix: oop

courses/advanced/02-oop/README.md

@@ -0,0 +1,232 @@
+# Introduction to Object-Oriented Programming
+
+C++ in a language that keeps evolving and adding new features. The language is now a multi-paradigm language, which means that it supports different programming styles, and we are going to cover the Object-Oriented Programming (OOP) paradigm in this course.
+
+## What is OOP?
+
+Object-Oriented Programming is a paradigm that encapsulate data and their interactions into a single entity called object. The object is an instance of a class, which is a blueprint for the object. The class defines the data and the operations that can be performed on the data.
+
+## Class declaration
+
+Here goes a simple declaration of a class Greeter:
+
+```cpp title="Greeter.h"
+#include <string>
+class Greeter {
+    std::string name;
+public:
+    Greeter(std::string username) {
+        name = username;
+    }
+    void Greet(){
+        std::cout << "Hello, " << name << "!" << std::endl;
+    }
+};
+```
+
+```cpp title="main.cpp"
+#include "Greeter.h"
+int main() {
+    Greeter greeter("Stranger");
+    greeter.Greet();
+}
+```
+
+If you run this code, the output will be:
+
+```bash
+Hello, Stranger!
+```
+
+Here goes a rework of the previous example using more robust concepts and multiple files:
+
+```cpp title="Greeter.h"
+#include <string>
+class Greeter {
+    // class members are private by default
+    std::string name;
+public:
+    // public constructor
+    // explicit to avoid implicit conversions
+    // const to avoid modification
+    // ref to avoid copying
+    explicit Greeter(const std::string& name);
+    ~Greeter(); // public destructor
+    void Greet(); // public method
+};
+```
+
+```cpp title="Greeter.cpp"
+#include "Greeter.h"
+#include <iostream>
+// :: is the scope resolution operator
+Greeter::Greeter(const std::string& name): name(name) {
+    std::cout << "I exist and I received " << name << std::endl;
+}
+Greeter::~Greeter() {
+    std::cout << "Goodbye, " << name << "!" << std::endl;
+}
+void Greeter::Greet() {
+    std::cout << "Hello, " << name << "!" << std::endl;
+}
+```
+
+```cpp title="main.cpp"
+#include "Greeter.h"
+int main() {
+    Greeter greeter("Stranger");
+    greeter.Greet();
+    // cannot use greeter.name because it is private
+}
+```
+
+## Advantages of OOP
+
+### Modularity
+
+Classes can be used it in different parts of your code. You can even create libraries and share it with other people.
+
+### Encapsulation
+
+Classes can hide their implementation details from the developer. The developer only needs the header file to use the class which acts as an interface.
+
+### Inheritance
+
+Classes can inherit from other classes. This allows you to reuse code and extend the functionality of existing classes expanding the original behavior. 
+
+We will cover details about inheritance in another moment.
+
+### Polymorphism
+
+By its roots, the word polymorphism means "many forms". It can be applied to classes in many different aspects:
+
+- **Function overload**: Class can have multiple definitions of the same member function, and the compiler will choose the correct one based on the type of the object.
+- **Casting**: Classes can be casted to other classes. This allows you to treat an object of a derived class as an object of its base class, or more complex behaviors;
+
+We will cover details about polymorphism in another moment.
+
+## Class internals
+
+### Constructors
+
+Constructors are special methods, they are called when an object is created, and don't return anything. They are used to initialize the object. If you don't define a constructor, the compiler will generate a default constructor for you.
+
+```c++
+class Greeter {
+    std::string name;
+public:
+    Greeter(const std::string& name) {
+        this->name = name;
+    }
+};
+```
+
+#### Default constructor
+
+A default constructor should be one of the following:
+- A constructor that can be called with no arguments; 
+- A constructor that can be called with default arguments;
+
+```c++
+class Greeter {
+    std::string name;
+public:
+    // Default constructor
+    Greeter() {
+        this->name = "Stranger";
+    }
+};
+```
+
+or
+
+```c++
+class Greeter {
+    std::string name;
+public:
+    Greeter(const std::string& name = "Stranger") {
+        this->name = name;
+    }
+};
+```
+
+If no constructor is defined, the compiler will generate a default constructor for you.
+
+#### Copy constructor
+
+A copy constructor is a constructor that takes a reference to an object of the same type as the class. It is used to initialize an object with another object of the same type.
+
+```c++
+class Greeter {
+    std::string name;
+public:
+    Greeter(const Greeter& other) {
+        this->name = other.name;
+    }
+};
+```
+
+#### Move constructor
+
+A move constructor is a constructor that takes a reference to an object of the same type as the class. It is used to initialize an object with another object of the same type. The difference between a copy constructor and a move constructor is that the move constructor takes ownership of the data from the other object, while the copy constructor copies the data from the other object.
+
+```c++
+class Greeter {
+    std::string name;
+public:
+    Greeter(Greeter&& other) {
+        this->name = std::move(other.name);
+    }
+};
+```
+
+#### Explicit constructor
+
+A constructor that can be called with only one argument is called an explicit constructor. This means that the compiler will not allow implicit conversions to happen.
+
+Explicit constructors are useful to avoid unexpected behavior when calling the constructor.
+
+```c++
+class Greeter {
+    std::string name;
+public:
+    explicit Greeter(const std::string& name) {
+        this->name = name;
+    }
+};
+```
+
+### Destructors
+
+Destructors are special methods, they are called when an object is destroyed.
+
+Following the **single responsibility principle**, the destructor should be responsible for cleaning up the dynamically allocated data the object is holding.
+
+If no destructor is defined, the compiler will generate a default destructor for you that might not be enough to clean up the data.
+
+```c++
+class IntContainer {
+    int* data;
+    // other members / methods
+public:
+    // other members / methods
+    ~IntContainer() {
+        // deallocate data
+        delete[] data;
+    }
+};
+```
+
+### Private and Public
+
+By default, all members of a class are private. This means that they can only be accessed by the class itself. If you want to expose a member to the outside world, you have to declare it as public.
+
+```c++ 
+class Greeter {
+    std::string name; // private by default
+public:
+    Greeter(const std::string& name) {
+        this->name = name;
+    }
+};
+```

mkdocs.yml

@@ -37,9 +37,10 @@ nav:
       - Sorting: courses/intro/10-sorting/README.md
   - Adv. Programming:
       - courses/advanced/README.md
-      - Introduction to C++:
+      - Advanced C++:
           - courses/advanced/01-introduction/README.md
           - Setup: courses/advanced/01-introduction/setup.md
+      - OOP: courses/advanced/02-oop/README.md
   - Algorithms:
       - courses/algorithms/README.md
       - Introduction to Algorithms: courses/algorithms/01-introduction/README.md