17.8. Classes and Objects: Association between classes

In programming, one of the most fundamental parts is the concept of classes and objects. This is a crucial concept for understanding logic programming and is one of the main topics in the Complete Course in Logic Programming for Beginners. In this chapter, we will focus specifically on association between classes.

To begin with, let's define what classes and objects are. A class is a model or blueprint that describes the variables and methods common to all objects of a certain kind. In the programming world, classes are used to create new objects (instances of a class). An object, on the other hand, is an instance of a class. It has state (stores values ​​in variables) and behavior (executes methods).

For example, think of a class as a sketch for a house. The sketch contains all the information needed to build a house, but it is not a house itself. When you build a house from scratch, that house is an object.

Now, let's get to the concept of association between classes. An association is a relationship between two or more classes that allows one class to know the properties and methods of the other. There are three types of associations: unidirectional, bidirectional, and self-association.

In one-way association, one class (the source class) has a relationship with another class (the target class), but the target class does not have a relationship with the source class. For example, imagine a class called Person and another class called Car. If the Person class has a field called Car, then there is a one-way association from the Person class to the Car class.

In bidirectional association, both classes have a relationship with each other. Using the same example as above, if the Car class also has a field called Person, then there is a bidirectional association between the Person and Car classes.

Self-association occurs when a class has a relationship with itself. For example, a class called Person might have a field called parent, which is also an instance of the Person class.

Association between classes is a fundamental concept in object-oriented programming because it allows objects to interact with each other in complex ways. For example, in a database program, you might have classes for Customers, Accounts, and Transactions. The Customer class can have an association with the Account class (a customer has one or more accounts), and the Account class can have an association with the Transaction class (an account has one or more transactions). These associations allow you to create programs that accurately reflect the complex realities of the business world.

To conclude, association between classes is a key concept in programming logic that allows objects to interact with each other in complex ways. It's a topic that takes practice and study to master, but once understood, it opens up a wide range of possibilities for software development.

This is just a glimpse of what you will learn in the Complete Logic Programming Course for Beginners. We hope this chapter has piqued your interest and encourages you to keep learning about this fascinating world of programming.

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