The Vala Language

GObject based programming language

What is this all about

Vala is an object-oriented programming language with a self-hosting compiler that generates C code and uses the GObject system. The wikipedia article

Vala, how does it work?

Language features

A simple example

					use Glib;

					class Sample : Glib.Object {
						void greeting() {
						    stdout.printf("Hello World\n");
						}

						static void main(string[] args) {
						    var sample = new Sample();
						    sample.greeting();
						}
					}
		    	

Compile with:

					valac sample.vala
		    	

A bit more advanced

					using Gtk;
 
					int main (string[] args) {
					    Gtk.init(ref args);
					 
					    var window = new Window();
					    window.title = "Hello, World!";
					    window.border_width = 10;
					    window.window_position = WindowPosition.CENTER;
					    window.set_default_size(350, 70);
					    window.destroy.connect(Gtk.main_quit);
					 
					    var label = new Label("Hello, World!");
					 
					    window.add(label);
					    window.show_all();
					 
					    Gtk.main();
					    return 0;
					}
		    	

Compile with:

					valac --pkg gtk+3.0 hellogtk.vala
		    	

But is it fast?

Yes, yes it is.

But what about libraries?

That's one of the main features of Vala,
Vapi bindings:

			[CCode (gir_namespace = "Gtk", gir_version = "2.0")]
			namespace Gtk {
				[CCode (cheader_filename = "gtk/gtk.h")]
				public class Dialog : Gtk.Window, Atk.Implementor, Gtk.Buildable {
					public Gtk.HButtonBox action_area;
					public weak Gtk.Widget separator;
					public Gtk.VBox vbox;
					[CCode (has_construct_function = false, type = "GtkWidget*")]
					public Dialog ();
				}
			}
		    	

Which libraries already have support?

Gtk, Gdk, Glib, Gio
Gstreamer
Libecal
Libnotify
Cairo
Sqlite/Sqlheavy
Mysql
Telepathy
Purple
Zeitgeist
Unity

But i don't like the syntax

Genie exists for people accustomed to Python.

				[indent=4]
				uses 
				    Gtk

				init
				    Gtk.init (ref args)
				    
				    var test = new TestWindow ()
				    test.show_all ()

				    Gtk.main ();

				class TestWindow : Window
				    init
				        title = "Test Window"
				        default_height = 250
				        default_width = 250

				        window_position = WindowPosition.CENTER
				        destroy += Gtk.main_quit

				        var button = new Button.with_label ("Click Me")
				        button.clicked += def (btn)
				            title = "Hello World"
				            btn.label = "Hello World"
				        add (button)
				

When should you use Vala?

In theory, practically everywhere
But currently mostly for desktop development (mainly Gnome)
Application needs to be fast, really fast

It can't all be fun and games

Still under heavy development
A lot of documentation but it is brief, cryptic

Who uses Vala?

Gnome
elementary OS
Zeitgeist
Shotwell
Geary

Many others...

But there is more...

GObject-Introspection
Plain C in Vala source files
Compile preprocessing
Etc...

Vala Project
Valadoc
Vala FAQ

Interested in Vala development?

Want to help a project in need?

elementary OS could use you!

Questions?