Why GtkWidget is not being found - gtk

Question

I have following simple application which creates a window with Label, Entry and Button:
using Gtk;
public static int main(string[] args) {
Gtk.init(ref args);
var mywin = new MyWindow("Entrypad");
mywin.show_all();
Gtk.main();
return 0;
}
public class MyWindow : Window{
public MyWindow(string stitle) {
this.title = stitle;
this.destroy.connect(Gtk.main_quit);
var grid = new Grid();
this.add(grid);
var lab = new Label("Mylabel:");
lab.set_xalign(1);
grid.attach(lab, 0, 0, 1, 1 );
Entry ent = new Entry();
grid.attach(ent, 1, 0, 1, 1 );
var printButton = new Button.with_label("Print Button");
grid.attach(printButton, 0, 1, 1, 1);
printButton.clicked.connect( printButtonFn );
}
}
private void printButtonFn(){
print("In print fn; \n");
}
Above code compiles and works all right. However, I want to show a dialog box, hence I modify printButtonFn and add code taken from here:
private void printButtonFn(){
print("In print fn; \n");
quick_message(this, "Message for dialog box.");
}
// Function to open a dialog box with a message
void quick_message (GtkWindow *parent, gchar *message) {
GtkWidget *dialog, *label, *content_area;
GtkDialogFlags flags;
flags = GTK_DIALOG_DESTROY_WITH_PARENT;
dialog = gtk_dialog_new_with_buttons ("Message",
parent,
flags,
_("_OK"),
GTK_RESPONSE_NONE,
NULL);
content_area = gtk_dialog_get_content_area (GTK_DIALOG (dialog));
label = gtk_label_new (message);
g_signal_connect_swapped (dialog,
"response",
G_CALLBACK (gtk_widget_destroy),
dialog);
gtk_container_add (GTK_CONTAINER (content_area), label);
gtk_widget_show_all (dialog);
}
However, above is giving error:
$ valac --pkg gtk+-3.0 mysrc.vala
rnskeletalGUI_dialog_soques.vala:50.21-50.21: error: syntax error, expected identifier
GtkWidget *dialog, *label, *content_area;
^
Compilation failed: 1 error(s), 0 warning(s)
Where is the problem and how can it be solved?

Answer 1

Two problems.
First, it's Gtk.Widget not GtkWidget. Or, if you have a using Gtk; in that code too, you can just use Widget.
Second, and the one valac is erroring about, is that unlike C, in Vala the pointer goes with the type, not the variable. So if you want three pointers to Gtk.Widget you should write GtkWidget* dialog, label, content_area; not Gtk.Widget *dialog, *label, *content_area;
That said, you shouldn't be using pointers here. Pointers in Vala basically opt you out of the memory management system, and you should almost never use them... think of it a bit like the "unsafe" keyword in some languages.