Object-Oriented Programming Basics

Objects

• An object is a real-world entity characterized by Reference/Identity, Behavior, & Property.
• Objects serve as the fundamental unit in object-oriented programming, encapsulating both data and functions.
• An object is an instance of a class, similar to how a cake is an instance of a recipe.
• Each object created from a class inherits attributes and behaviors defined in the class.

Classes

• A class is a collection or template of objects, acting as a blueprint that defines properties and behaviors.
• Classes establish the structure, behavior, and attributes that an object will have.
• To create a class, the class keyword is used, following a specific syntax.

Class Syntax

• The basic syntax for defining a class is:

  class class_name {
      // Access specifier;
      // Data member;
      // Member function / Methods;
  };
  

Access Specifiers

• Access specifiers control the visibility and accessibility of class members, enforcing data hiding.
• There are three primary types of access specifiers in C++:
  • Public: Members are accessible from anywhere in the program.
  • Private: Members are only accessible within the class itself.
  • Protected: Members are accessible within the class and its subclasses.

Access Specifier Syntax

• The syntax for defining access specifiers in a class:

  class ClassName {
      private:
          // Declare private members/methods here.
      public:
          // Declare public members/methods here.
      protected:
          // Declare protected members/methods here.
  };
  

Example Class

• An example of a simple class in C++:

  class MyClass {
      public:
          int publicVar;    // Accessible from anywhere
      private:
          int privateVar;   // Accessible only from within the class
      protected:
          int protectedVar; // Accessible from class and its subclasses
  
      public:
          // Constructor definition
          MyClass() { 
              publicVar = 1; 
              privateVar = 2; 
              protectedVar = 3; 
          }
  
          // Method to display values
          void displayValues() { 
              cout << "Public: " << publicVar << " Private: " << privateVar << " Protected: " << protectedVar; 
          }
  };
  

• The constructor initializes the properties of the object when an instance is created.