Re: [Vala] Idle.add lambda function with local variable

[Geert Jan <gj_alsem yahoo com>]

> > Ok I messed up that example, sorry. Obviously in my
> real project I do
> > create a main loop. Don't have time now, but unless
> someone can help me
> > despite my bad example I'll post the real code from my
> project later.
>
> Well, the point is not whether the main loop is created,
> but whether it's
> actually dispatching. If you call the Thread.usleep() from
> within a main loop,
> no idle handlers are going to run, because you didn't
> return to the main
> loop, so it can't do it's job. You have to return from the
> currently
> executing handler and than the idle handlers can run (the
> event dispatching
> is completely synchronous -- until one is completely
> handled, no other can
> be).
>
> Newer vala (since 0.7.7 IIRC) allows writing a single
> "async" function, that
> will be automatically split into parts that can be run from
> the mainloop at
> separate events, but you need to understand how the main
> loop behaves before
> you can use them anyway.

Thanks Jan, for that additional info. There are indeed still one or two things about threading that I could 
use some more practice with.

However, in the program I'm writing threading isn't the problem. I was wondering about using local variables 
in a lambda function, with the purpose of using them in a function that is added to Idle.

So now wrote a new (better) example and found out that it actually works:


public class Main : Object {

  public class MyObject : Object {
    public int x { get; set; }
  }

  public static void button_clicked () {
    MyObject o = new MyObject ();
    o.x = 3;
    Idle.add ( () => {
      print_myobject (o);
      return false;
    });
  }

  public static void print_myobject (MyObject o) {
    print ("%d\n", o.x);
  }

  public static int main (string[] args) {
    Gtk.init (ref args);

    Gtk.Button button = new Gtk.Button.with_label ("Click me");
    button.clicked.connect (Main.button_clicked);

    Gtk.Window window = new Gtk.Window (Gtk.WindowType.TOPLEVEL);
    window.destroy.connect (Gtk.main_quit);
    window.add (button);
    window.show_all ();

    Gtk.main ();
    return 0;
  }
}


The above works, it prints "3" everytime you click the button. However, when compiling, it still gives the 
error I posted about in my original post:


/media/Data/Code/Vala/valatest/lambda/main.vala.c: In function ‘main_button_clicked’:
/media/Data/Code/Vala/valatest/lambda/main.vala.c:131: warning: passing argument 4 of ‘g_idle_add_full’ from 
incompatible pointer type
/usr/include/glib-2.0/glib/gmain.h:291: note: expected ‘GDestroyNotify’ but argument is of type ‘void 
(*)(struct Block1Data *)’


I assumed I was doing something wrong when I saw this, but since the compiled program does work fine, I'm 
starting to think it's just a small bug in Vala.