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diff --git a/vala.html.markdown b/vala.html.markdown new file mode 100755 index 00000000..393578b0 --- /dev/null +++ b/vala.html.markdown @@ -0,0 +1,503 @@ +--- +language: vala +contributors: + - ["Milo Gilad", "https://github.com/Myl0g"] +filename: LearnVala.vala +--- + +In GNOME's own words, "Vala is a programming language that aims to bring modern programming language features to GNOME developers without imposing any additional runtime requirements and without using a different ABI compared to applications and libraries written in C." + +Vala has aspects of Java and C#, so it'll be natural to those who know either. + +[Read more here.](https://wiki.gnome.org/Projects/Vala) + +```vala + +// Single line comment + +/* Multiline +Comment */ + +/** +* Documentation comment +*/ + +/* Data Types */ + +char character = 'a' +unichar unicode_character = 'u' // 32-bit unicode character + +int i = 2; // ints can also have guaranteed sizes (e.g. int64, uint64) +uint j = -6; // Won't compile; unsigned ints can only be positive + +long k; + +short l; +ushort m; + +string text = "Hello,"; // Note that the == operator will check string content + +string verbatim = """This is a verbatim (a.k.a. raw) string. Special characters +(e.g. \n and "") are not interpreted. They may also be multiple lines long."""; + +// String Templates allow for easy string formatting +string string_template = @"$text world"; // "$text" evaluates to "Hello," + +int test = 5; +int test2 = 10; +string template2 = @"$(test * test2) is a number."; // Expression evaluation + +string template_slice = string_template[7:12]; // => "world" + +// Most data types have methods for parsing. + +bool parse_bool = bool.parse("false"); // => false +int parse_int = int.parse("-52"); // => -52 +string parse_string = parse_int.to_string(); // => "-52" + +/* Basic I/O */ + +stdout.printf(parse_string); // Prints to console +string input = stdin.read_line(); // Gets input from console + +stderr.printf("Error message"); // Error printing + +/* Arrays */ + +int[] int_array = new int[10]; // Array of ints with 10 slots +int better_int_array[10]; // Above expression, shortened +int_array.length; // => 10; + +int[] int_array2 = {5, 10, 15, 20}; // Can be created on-the-fly + +int[] array_slice = int_array2[1:3]; // Slice (copy of data) +unowned int[] array_slice_ref = int_array2[1:3]; // Reference to data + +// Multi-dimensional Arrays (defined with a number of commas in the brackets) + +int[,] multi_array = new int[6,4]; // 6 is the number of arrays, 4 is their size +int[,] multi_array2 = {{7, 4, 6, 4}, + {3, 2, 4, 6}, + {5, 9, 5, 1}}; // new int[3,4] +multi_array2[2,3] = 12; // 2 is the array, 3 is the index in the array +int first_d = multi_array2.length[0] // => 3 +int second_d = multi_array2.length[1] // => 4 + +// Stacked arrays (e.g. int[][]) where array lengths vary are not supported. + +// Multi-dimensional arrays cannot be sliced, nor can they be converted to one- +// dimensional. + +int[] add_to_array = {}; +add_to_array += 12; // Arrays can be dynamically added to + +add_to_array.resize(20); // Array now has 20 slots + +uint8[] chars = "test message".data; +chars.move(5, 0, 7); +stdout.printf((string) chars); // Casts the array to a string and prints it + +/* Control Flow */ + +int a = 1; +int b = 2; +int[] foreach_demo = {2, 4, 6, 8}; + +while (b > a) { // While loop; checks if expression is true before executing + b--; +} + +do { + b--; +} +while (b > a); // Do While loop; executes the code in "do" before while (b > a) + +for (a = 0; a < 10; a++) { stdout.printf("%d\n", a); } // for loop + +foreach (int foreach_demo_var in foreach_demo) { + stdout.printf("%d\n", foreach_demo_var); +} // foreach works on any iterable collection + +if (a == 0) { + stdout.printf("%d\n", a); +} else if (a > 1) { + stdout.printf("%d\n", a); +} else { + stdout.printf("A is less than 0"); +} // if-then-else + +switch (a) { + case 1: + stdout.printf("A is 1\n"); + break; + case 5: + case 10: + stdout.printf("A is 5 or 10\n"); + break; + default: + stdout.printf("???\n") + break; +} // switch statement + +/* Type Casting and Inference */ + +int cast_to_float = 10; +float casted_float = (float) cast_to_float; // static casting; no runtime checks + +// For runtime checks, use dynamic casting. +// Dynamically casted objects must be the following: +// - Object's class is the same class as the desired type +// - Object's class is a subclass of the desired type +// - Desired class is an interface implemented by the object's class + +float dyna_casted_float = cast_to_float as float // Won't compile + +var inferred_string = "hello"; // Type inference + +/* Methods (a.k.a. functions) */ + +int method_demo(string arg1, Object arg2) { // Returns int and takes args + return 1; +} + +// Vala methods cannot be overloaded. + +void some_method(string text) { } +void some_method(int number) { } // Won't compile + +// To achieve similar functionality, use default argument values. + +void some_better_method(string text, int number = 0) { } + +some_better_method("text"); +some_better_method("text", 12); + +// varargs (variable-length argument lists) are also supported. + +void method_with_varargs(int arg1, ...) { + var varargs_list = va_list(); // gets the varargs list + + string arg_string = varargs_list.arg(); // gets arguments, one after another + int int_vararg = varargs_list.arg(); + + stdout.printf("%s, %d\n", arg_string, int_vararg) +} + +string? ok_to_be_null(int? test_int) { } // "?" denotes possible null value + +// Delegates + +delegate void DelegateDemo(char char_a); + +void delegate_match(char char_a) { // Matches DelegateDemo's signature + stdout.printf("%d\n"); +} + +void call_delegate(DelegateDemo d, char char_b) { // Takes a delegate arg + d(char_b) // calls delegate +} + +void final_delegate_demo() { + call_delegate(delegate_match); // Passes matching method as argument +} + +// Lambdas (a.k.a. Anonymous Methods) are defined with "=>" + +(a) => { stdout.printf("%d\n", a); } // Prints "a" + +/* Namespaces */ + +namespace NamespaceDemo { + // Allows you to organize variable names + int namespace_int = 12; +} +namespace_int += 5; // Won't compile + +using NamespaceDemo; +namespace_int += 5; // Valid + +/* Structs and Enums */ + +struct Closet { + public uint shirts; // Default access modifier is private + public uint jackets; +} + +Closet struct_init_1 = Closet(); // or Closet struct_init_1 = {}; +Closet struct_init_2 = {15, 3}; +var struct_init_3 = Closet() { // Type inference also works + shirts = 15; + jackets = 3; +} + +enum HouseSize { // An example of an enum + SMALL, + MODERATE, + BIG +} + +/* Classes and Object-Oriented Programming */ + +class Message : GLib.Object { // Class Message extends GLib's Object + private string sender; // a private field + public string text {get; set;} // a public property (more on that later) + protected bool is_digital = true; // protected (this class and subclasses) + internal bool sent = false; // internal (classes in same package) + + public void send(string sender) { // public method + this.sender = sender; + sent = true; + } + + public Message() { // Constructor + // ... + } + +} + +// Since method overloading isn't possible, you can't overload constructors. +// However, you can use named constructors to achieve the same functionality. + +public class Calculator : GLib.Object { + + public Calculator() { + } + + public Calculator.with_name(string name) { + } + + public Calculator.model(string model_id, string name = "") { + this.with_name(@"$model_id $name"); // Chained constructors with "this" + } + ~Calculator() { } // Only needed if you're using manual memory management +} + +var calc1 = new Calculator.with_name("Temp"); +var calc2 = new Calculator.model("TI-84"); + +// Signals (a.k.a. events or event listeners) are a way to execute multiple +// methods with the same signature at the same time. + +public class SignalDemo : GLib.Object { + public signal void sig_demo(int sig_demo_int); // Must be public + + public static int main(string[] args) { + // main method; program does not compile without it + + var sig_demo_class = new SignalDemo(); // New instance of class + + sig_demo_class.sig_demo.connect((ob, sig_int) => { // Lambda used as handler + stdout.printf("%d\n", sig_int); // "ob" is object on which it is emitted + }); + + sig_demo_class.sig_demo(27); // Signal is emitted + + return 0; + } +} + +// You may use the connect() method and attach as many handlers as you'd like. +// They'll all run at around the same time when the signal is emitted. + +// Properties (getters and setters) + +class Animal : GLib.Object { + private int _legs; // prefixed with underscore to prevent name clashes + + public int legs { + get { return _legs; } + set { _legs = value; } + } + + public int eyes { get; set; default = 5; } // Shorter way + public int kingdom { get; private set; default = "Animalia"} // Read-only + + public static void main(string args[]) { + rabbit = new Animal(); + + // All GLib.Objects have a signal "notify" emitted when a property changes. + + // If you specify a specific property, replace all underscores with dashes + // to conform to the GObject naming convention. + + rabbit.notify["eyes"].connect((s, p) => { // Remove the ["eyes"] for all + stdout.printf("Property '%s' has changed!\n", p.name); + }); + + rabbit.legs = 2; + rabbit.legs += 2; + rabbit.eyes = 2; + + } +} + +// Inheritance: Vala classes may inherit 1 class. Inheritance is not implicit. + +class SuperDemo : GLib.Object { + public int data1; + protected int data2; + internal int data3; + private int data4; + + public static void test_method { } // Statics can be called w/out an object +} +class SubDemo : SuperDemo { + public static void main(string args[]) { + stdout.printf((string) data1); // Will compile + stdout.printf((string) data2); // Protected can be accessed by subclasses + stdout.printf((string) data3); // Internal is accessible to package + stdout.printf((string) data4); // Won't compile + } +} + +// Abstract Classes and Methods + +public abstract class OperatingSystem : GLib.Object { + public void turn_on() { + stdout.printf("Booted successfully.\n"); + } + public abstract void use_computer(); +} + +public class Linux : OperatingSystem { + public override void use_computer() { // Abstract methods must be overridden + stdout.printf("Beep boop\n"); + } +} + +// Add default behavior to an abstract method by making it "virtual". + +public abstract class HardDrive : GLib.Object { + public virtual void die() { + stdout.printf("CLICK-CLICK-CLICK\n"); + } +} +public class MyHD : HardDrive { + public override void die() { + return; + } +} + +// Interfaces: classes can implement any number of these. + +interface Laptop { // May only contain abstracts or virtuals + public abstract void turn_on(); + public abstract void turn_off(); + + public abstract int cores; // Won't compile; fields cannot be abstract + public abstract int cores {get; set;} // Will compile + + public virtual void keyboard() { // Virtuals are allowed (unlike Java/C#) + stdout.printf("Clickity-clack\n"); + } +} + +// The ability to use virtuals in Vala means that multiple inheritance is +// possible (albeit somewhat confined) + +// Interfaces cannot implement interfaces, but they may specify that certain +// interfaces or classes must be also implemented (pre-requisites). + +public interface CellPhone : Collection, GLib.Object {} + +// You can get the type info of a class at runtime dynamically. + +bool type_info = object is TypeName; // uses "is" to get a bool + +Type type_info2 = object.get_type(); +var type_name = type_info2.name(); + +Type type_info3 = typeof(Linux); +Linux type_demo = (Linux) Object.new(type_info3); + +// Generics + +class Computer<OperatingSystem> : GLib.Object { + private OperatingSystem os; + + public void install_os(OperatingSystem os) { + this.os = os; + } + public OperatingSystem retrieve_os() { + return this.os; + } +} + +var new_computer = new Computer<Linux>(); + +/* Other Features */ + +// Assertions: crash if a statement is not true (at runtime) + +bool is_true = true; +assert(is_true); + +// Contract Programming + +int contract_demo(int arg1, int arg2) { + requires(arg1 > 0 && arg1 < 10) // Notice the lack of semicolon + requires(arg2 >= 12) + ensures(result >= 0) +} + +// Error Handling + +void error_demo(int int_ex) throws GError { + if (int_ex != 1) { + throw new GError("TEST MESSAGE"); + } +} +void error_demo2() { + try { + error_demo(0); + } catch (GError ge) { + stdout.printf("%s\n", ge.message); + } +} + +// Main Loop + +void main() { + + var main_loop = new MainLoop(); + var time = new TimeoutSource(2000); + + time.set_callback(() => { // Executes the following lambda after 2000ms + stdout.printf("2000ms have passed\n"); + main_loop.quit(); + return false; + }); + + time.attach(main_loop.get_context()); + + loop.run(); +} + +// Pointers (manual memory management) + +Object* pointer_obj = new Object(); // Creates Object instance and gives pointer + +pointer_obj->some_method(); // Executes some_method +pointer_obj->some_data; // Returns some_data + +delete pointer_obj; + +int more = 57; +int* more_pointer = &i; // & = address-of +int indirection_demo = more_pointer*; // indirection + +// Profiles: affect which Vala features are avaliable and which libraries the +// C-code will use. +// - gobject (default) +// posix +// dova +// Use "--profile=whatever" when compiling. + +``` +* More Vala documentation can be found [here](https://valadoc.org/). +* [Alternate construction syntax](https://wiki.gnome.org/Projects/Vala/Tutorial#GObject-Style_Construction) similar to GObject +* More on contract programming [here](http://en.wikipedia.org/wiki/Contract_programming) +* Collections library can be found [here](https://wiki.gnome.org/Projects/Vala/Tutorial#Collections) +* [Multithreading](https://wiki.gnome.org/Projects/Vala/Tutorial#Multi-Threading) +* Read about building GUIs with GTK+ and Vala [here](http://archive.is/7C7bw). +* D-Bus [integration](https://wiki.gnome.org/Projects/Vala/Tutorial#D-Bus_Integration) |