Classes & Objects

Key Concepts

Review core concepts you need to learn to master this subject

Class Members

Access Control Operators

Objects

Constructor

Destructor

Class Members

class City {

  // attribute
  int population;

public:
  // method
  void add_resident() {
    population++;
  }

};

A C++ class is comprised of class members:

Attributes, also known as member data, consist of information about an instance of the class.
Methods, also known as member functions, are functions that can be used with an instance of the class.

Access Control Operators

class City {

  // attribute
  int population;

public:
  // method
  void add_resident() {
    population++;
  }

};

C++ classes have access control operators that designate the scope of class members:

public
private

public members are accessible everywhere; private members can only be accessed from within the same instance of the class or from friends classes.

Objects

class City {

  // attribute
  int population;

public:
  // method
  void add_resident() {
    population++;
  }

};

In C++, an object is an instance of a class that encapsulates data and functionality pertaining to that data.

Constructor

class City {

  // attribute
  int population;

public:
  // method
  void add_resident() {
    population++;
  }

};

For a C++ class, a constructor is a special kind of method that enables control regarding how the objects of a class should be created. Different class constructors can be specified for the same class, but each constructor signature must be unique.

Destructor

class City {

  // attribute
  int population;

public:
  // method
  void add_resident() {
    population++;
  }

};

For a C++ class, a destructor is a special method that handles object destruction, generally focused on preventing memory leaks. Class destructors don’t take arguments as input and their names are always preceded by a tilde ~.

Classes and Objects

Lesson 1 of 1

1
So far, we’ve used several data types, including int, double, std::string, and bool. When we work with int or std::string, we can create variables with certain properties and methods specific to th…
2
An empty class is pretty useless. Classes are designed to bring together related information and functionality — time to add stuff inside! Components of a class are called class members. Just l…
3
Now that you have a class, let’s create some objects! To refresh your memory, an object is an instance of a class, which encapsulates data and functionality pertaining to that data. To create (or …
4
Let’s circle back to that public keyword. What was that about? By default, everything in a class is private, meaning class members are limited to the scope of the class. This makes it easier to ke…
5
Is there a way to give an object some data right when it gets created? We’re so glad you asked! A constructor is a special kind of method that lets you decide how the objects of a class get crea…
6
So far, you’ve learned how to create and use objects. But there’s another part of the object lifecycle we need to cover: how to destroy them! Muahahaha. It’s actually far less nefarious than it so…
7
Hooray! You’ve learned the basics of classes and objects in C++: - Classes are user-defined types. - Objects are instances of classes. - Class members are the data attributes and functions inside o…