17. Classes and Objects

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17. Classes and Objects

In object-oriented programming, Classes and Objects are fundamental concepts. We will better understand each of them in this chapter.

Classes

A class can be thought of as a model, a sketch, or a blueprint from which objects are created. It defines the characteristics (attributes) and behaviors (methods) that an object of the type defined by it will have. A class is like a blueprint for creating objects.

For example, we might have a class called "Car" that defines attributes such as make, model, color, year, etc. and methods such as turning on, off, accelerating, braking, etc. A class is therefore an abstract definition of a type of object.

Objects

An object is an instance of a class. In other words, it is a concrete realization of a class. Each object has a state and behavior defined by the attributes and methods of its class.

Using the example of the "Car" class, an object of this class could be a specific car, such as a "Ferrari 458 Italia red, year 2015". This object has a state defined by the values ​​of its attributes (brand = Ferrari, model = 458 Italia, color = red, year = 2015) and a behavior defined by the methods it can execute (on, off, accelerating, braking).

Relationship between Classes and Objects

The relationship between classes and objects is one of "instance-type". A class is a type of thing, while an object is an instance of that type. For example, "Car" is a type of thing, while a "Red-colored Ferrari 458 Italia, year 2015" is an instance of that type.

Creating Classes and Objects

In most object-oriented programming languages, a class is defined using the "class" keyword, followed by the class name and a block of code delimited by braces ({}) that define its attributes and methods.

For example, in Java, the "Car" class could be defined as follows:

class Car {
  String tag;
  model string;
  String color;
  int year;

  void call() {
    // code to start the car
  }

  void disconnect() {
    // code to turn off the car
  }
}

An object is created from a class using the "new" keyword, followed by the class name and a pair of parentheses (). The result is a reference to an object of the class, which can be assigned to a variable.

For example, in Java, an object of class "Car" could be created as follows:

Car myCar = new Car();

Object attributes can be initialized or accessed using dot (.) notation, followed by the attribute name. Object methods can be called in the same way.

myCar.brand = "Ferrari";
myCarro.model = "458 Italia";
myCar.color = "red";
myCar.year = 2015;

myCar.call();

Conclusion

Classes and objects are fundamental concepts in object-oriented programming. A class defines a type of object, while an object is an instance of a class. Learning to create and use classes and objects is a crucial step in becoming an effective programmer.

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4517.1. Classes and Objects: Introduction to Classes and Objects