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Intro to OOP Cheat Sheet (DRAFT) by

Object-Oriented Programming (OOP) is a programming paradigm that organizes code into objects, which combine data (attributes) and functions (methods). OOP promotes modularity, reusability, and scalability, making complex software easier to develop and maintain.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Class and Objects

Class
A user-d­efined data type that defines attributes (data members) and behaviors (member functi­ons). It acts as a blueprint for objects
Object
An instance of a class with specific values and behaviors

Pillars of OOP

Encaps­ulation
Encaps­ulation is wrapping up the data and methods together within a single entity. In C++, classes are used for encaps­ula­tion.
Abstra­ction
Showing only the necessary details and hiding the internal details is known as abstra­ction.
Polymo­rphism
Providing different functi­ona­lities to the functions or operators of the same name is known as Polymo­rphism.

Access Specifiers

• public: Accessible from outside the class.
• private: Cannot be accessed directly from outside.
• protected: Like private, but accessible in derived classes.

class Demo {
private:
int secret­Number;
public:
int public­Number;
};

Class Example

class Car {
public:
    string brand;
    int year;
};

int main() {
    Car myCar;
    myCar.brand = "Toyota";
    myCar.year = 2022;
}
 

Inheri­tance

Deriving the properties of a class ( Parent class ) to another class ( Child class ) is known as Inheri­tance. It is used for code reusab­ilty.

Building a Class

Attribute (Data Members)
variables which represent the attributes of the class
Functi­onality (Member Functions)
functions which represent the behaviors of the class

Constr­uctor

a special member function that is automa­tically called when an object of a class is created

Object Instan­tiation

• Creating objects from a class.
• Accessing attrib­ute­s/m­ethods using dot syntax.
Circle c1(5.0);
cout << c1.radius;

Demons­tration

Compute circumference and area of a circle.

class Circle {
private:
    double radius;
public:
    Circle(double r) { radius = r; }
    double getCircumference() { return 2  3.1416  radius; }
    double getArea() { return 3.1416  radius  radius; }
};

int main() {
    Circle c1(5);
    cout << "Circumference: " << c1.getCircumference();
    cout << "Area: " << c1.getArea();
}

Class Rectangle

class Rectangle {
public:
    int length, width;
    int area() {
        return length * width;
    }
};