listmodel.rb

require 'gtk3'

class Model < GLib::Object
  type_register

  include Gio::ListModel

  def initialize
    super

    @array = ["apple", "banana", "orange"] * 10
  end

  def do_get_item_type
    GLib::STRING
  end

  def do_get_n_items
    @array.length
  end

  def do_get_item(pos)
    @array[pos]
  end
end

listbox = Gtk::ListBox.new
model = Model.new
listbox.bind_model model do |item|
  Gtk::Label.new item
end

window = Gtk::Window.new
window << listbox
window.show_all

Gtk.main