chapter1.md

Vala C code generator

Vala provides valac, a tool to translate Vala code to C.

All C code uses GLib, GObject and GInterface, to provides Object Oriented Programming capabilites. If haven't that libraries yet, install them first.

All your generated code will follow GObject Conventions, in order to provide consistent API between libraries using this GNOME technology. If you read them first, you can avoid common errors.

valac just produce valid C code if you follow a GObject Conventions and take in account the ones described in this chapter.

Class Names

All your classes's name should use CamelCase convention. Don't use underscope _ , they are used to separate methods names.

Interfaces Names

Use same conventions as instantiable classes, because they at the end are types and classes, but un-instantiable.

Namespaces

All your classes should be in a namespace both using namespace clause or prefixing your class name at declaration time.

public Prx.YourClass : Object {}

In above example, YourClass is a class name with a prefix Prx. In C it will use PrxYourClass as type name.

If you generate code without namespaces, is possible to produce invalid C code without notice.

Class Methods

All methods declared as part of a class declaration, are prefixed using lower case name of class and _ as a separator.

public Prx.YourClass : Object {
    public void method () {}
}

method as a C code will be: prx_yourclass_method.

Large methods names should use _ as separators, avoid CamelCase syntax, because its against GObject method conventions.

public Prx.YourClass : Object {
    public void method_name () {}
}

method_name_as a C code will be: _prx_your_class_method_name.

Class Properties

Class or interface properties should use lowercase names. Long names should use _ as word separator.

public class Exm.Letter {
    public string name { get; set; }
    public int vertical_size { get; set; }
}

Properties's accessors in C for above methods are exm_letter_get_name() and exm_letter_get_vertical_size(), this is why you can't use type as a property name; it will be mapped to exm_letter_get_type(), according with GObject C coding conventions it should be used to register and return object's type and Vala create one for your class automatically; at the end you'll have two methods of the same name at C compilation time.

var keyword

var keyword is a short way to declare new variables and should be used on typed declaration: a typed return value from a method, a variable or constant. Typed variables shoud be used in Vala and is recommended, but valid, to declare a variable as var l = null this declaration use gpointer as variable type, in Vala may have no sense but in C.