Chapter7: Understanding Data and Methods

Chapter 7: Understanding Data and Methods in Vala Applications

7.1 Introduction

Every application, at its core, is a combination of data and the methods that operate on that data. In this chapter, we will explore how this fundamental concept is implemented in Vala, a modern and powerful programming language. Through examples, we'll understand how data is structured and how methods manipulate this data to perform meaningful tasks.

7.2 Data in Vala: Types and Structures

In Vala, data is represented through various types, such as primitive data types, classes, and structs.

Primitive Data Types: These include int, float, double, string, bool, etc. They represent the simplest forms of data.


int number = 10;

string message = "Hello, Vala!";

bool isActive = true;

Classes: Classes are blueprints for creating objects (instances) and encapsulate data and methods. They represent complex data types.


public class Person {

    public string name;

    public int age;

    public Person(string name, int age) { = name;

        this.age = age;



Person person = new Person("Alice", 30);

Structs: Structs are similar to classes but are value types and usually used for smaller and simpler data structures.



Copy code

public struct Point {

    public int x;

    public int y;


Point point = {x: 10, y: 20};

7.3 Methods in Vala

Methods are blocks of code that perform operations on data. In Vala, methods can be part of classes or structs, or they can be standalone functions.

Methods in Classes: They operate on the data contained within class instances (objects).


public class Calculator {

    public int add(int a, int b) {

        return a + b;



Calculator calc = new Calculator();

int result = calc.add(5, 3);

Standalone Functions: Functions that are not part of any class or struct, but can still operate on data passed to them.


int multiply(int a, int b) {

    return a * b;


int product = multiply(4, 2);

7.4 Working with Data and Methods Together

The real power of programming is evident when methods operate on data. Let's see a more complex example that combines both:


public class Book {

    public string title;

    public string author;

    public int pages;

    public Book(string title, string author, int pages) {

        this.title = title; = author;

        this.pages = pages;


    public void printDetails() {

        stdout.printf("Book: %s by %s, Pages: %d\n", title, author, pages);



void main() {

    Book myBook = new Book("Vala Programming", "Jane Doe", 300);



In this example, the Book class encapsulates the data related to a book (title, author, and pages) and provides a method printDetails() to display this information.

7.5 Conclusion

Understanding how data and methods work together is crucial in Vala, as in any other programming language. Data represents the state, and methods define the behavior or operations that can be performed on this data. Mastering the use of data and methods is key to building functional and efficient applications in Vala.

This chapter aims to provide beginners with a clear understanding of how data and methods form the basis of Vala applications. The examples are designed to illustrate these concepts in a simple yet effective manner, paving the way for more complex programming in subsequent chapters.