Re: [Vala] getting started with vala and glade

[Luc Chante <luc chante gmail com>]

Hi,

Just to reply to :
"...
- For setting properties on the parent in a constructor what is wrong with
   this.property_name = xyz;
..."
It is not wrong, but the behaviour is not exactly the same.

I get stuck on this before I realize the error.
When you use the constructed() method (to initialize ui by exemple), if you
use "this.something = some_arg", something isn't initialized in the
constructed() method, but it is when you use Object(something: some_arg).

Approximative generated C code for a class "Ns.ClassName" without Object()
call in the constructor :

NsClassName* ns_class_name_construct (GType object_type, type some_arg) {
    NsClassName * self = NULL;
    ...
    self = (NsClassName*) g_object_new (object_type, NULL);
    ...
    ns_class_name_set_something (self, some_arg);
    ...
    return self;
}

the constructed() method is called at the end of g_object_new(), so
ns_class_name_set_something() isn't called yet.

Same thing with a the use of Object() :

NsClassName* ns_class_name_construct (GType object_type, type some_arg) {
    NsClassName * self = NULL;
    ...
    self = (NsClassName*) g_object_new (object_type, "something", some_arg,
NULL);
    ...
    return self;
}

In this case, when the constructed() method is called something has the
value some_arg.

Regards,
Luc.

Le lun. 27 juin 2016 à 17:30, Al Thomas <astavale yahoo co uk> a écrit :

> ------------------------------
> *From:* Luc Chante <luc chante gmail com>
> *Sent:* Monday, 27 June 2016, 11:36
> *Subject:* Re: [Vala] getting started with vala and glade
>
>
> I think it would be a good start to use gtk templates.
> So you can use your ui file and create the ApplicationWindow by it's
> constructor (which takes an Application instance).
>
> Join to this mail a really simple example using ui file and gtk templates.
> Tested with msys 2.
>
> This is a great start for a code sample on the wiki, maybe:
> https://wiki.gnome.org/Projects/Vala/GTKTemplateSample
>
> As a code sample I have a couple of doubts about the current coding style:
>
>  - I think the main() method should be on its own, not buried in an object
>
>  - For setting properties on the parent in a constructor what is wrong with
>    this.property_name = xyz;
>    instead of using Vala specific GObject plumbing like Object(
> property_name: value );
>   Although these low level GObject features exist they add additional
> complexity when
>   initially learning the language and are unnecessary in most cases
>
> So a revised main.vala:
>
> /**
>  * Application
>  */
> public class MyApplication : Gtk.Application
> {
>     public MyApplication(string? app_id = null, ApplicationFlags flags =
> ApplicationFlags.FLAGS_NONE)
>     {
>     if (app_id != null && Application.id_is_valid (app_id) == false) {
>         error( "Application ID is not valid");
>     }
>     this.application_id = app_id;
>     this.flags = flags;
>     }
>
>     public override void activate () {
>         var window = new Template.ApplicationWindow (this);
>         window.present ();
>     }
> }
>
> /**
>  * Application window
>  */
> [GtkTemplate(ui = "/template/window.ui")]
> public class Template.ApplicationWindow : Gtk.ApplicationWindow
> {
>     [GtkChild]
>     Gtk.Button test_button;
>
>     public ApplicationWindow(Gtk.Application application)
>     {
>         this.application = application;
>     }
>
>     [GtkCallback]
>     public void on_test_button_clicked(Gtk.Button button)
>     {
>         GLib.message("Button clicked !!!");
>     }
> }
>
> /** Application entry point */
> public static int main(string[] args)
> {
>     var app = new MyApplication ("my.application");
>     return app.run (args);
> }
>
> Finally as a more generic way to compile use:
>
> glib-compile-resources --sourcedir ./ --generate-source --target
> resources.c template.gresource.xml
> valac --pkg gtk+-3.0 --target-glib 2.38 --gresources
> template.gresource.xml resources.c main.vala --output myapp
>
> The Makefile is nice though.
>
> Regards,
>
> Al