Demo Code on main page showing click not found

Question

I am trying to compile demonstration code on the main page of Vala programming language

int main (string[] args) {
  var app = new Gtk.Application(
    "com.example.App",
    ApplicationFlags.FLAGS_NONE
  );
  
  app.activate.connect(() => {
    var win = new Gtk.ApplicationWindow(app);

    var btn = new Gtk.Button.with_label("Hello World");
    btn.click.connect(win.close);

    win.child = btn;
    win.present();
  });
  return app.run(args);
} 

I am using following command:

$ valac --pkg gtk+-3.0 valademo.vala 

However, it is giving following error:

valademo.vala:13.5-13.13: error: The name `click' does not exist in the context of `Gtk.Button'
    btn.click.connect(win.close);
    ^^^^^^^^^
Compilation failed: 1 error(s), 0 warning(s)

Where is the problem and how can it be solved?

Answer 1

That's probably a typo, it should be clicked not click. You may want to raise an issue with the website or submit a pull request.

There are a couple of other problems. Firstly GTK+3 needs win.show_all(), but that has been removed in GTK 4.

Secondly the documentation for win.present() is advising that function shouldn't be used.

Here's a working example for GTK+3:

int main (string[] args) {
  var app = new Gtk.Application(
    "com.example.App",
    ApplicationFlags.FLAGS_NONE
  );

  app.activate.connect(() => {
    var win = new Gtk.ApplicationWindow(app);

    var btn = new Gtk.Button.with_label("Hello World");
    btn.clicked.connect(win.close);

    win.child = btn;
    win.show_all();
  });
  return app.run(args);
}