All of the code associated with the FXRuby extension is provided by the fxruby gem, so we need to start by requiring this gem:

require 'rubygems'
require_gem 'fxruby'

Since all of the FXRuby classes are defined under the Fox module, you'd normally need to refer to them using their "fully qualified" names (i.e. names that begin with the Fox:: prefix). Because this can get a little tedious, and because there's not really much chance of name conflicts between FXRuby and other Ruby extensions, I usually like to add an include Fox statement so that all of the names in the Fox module are "included" into the global namespace:

require 'rubygems'
require_gem 'fxruby'

include Fox

Every FXRuby program begins by creating an FXApp instance:

require 'rubygems'
require_gem 'fxruby'

include Fox

theApp = FXApp.new

The FXApp instance has a lot of responsibilities in an FXRuby application. One of the most frequent ways you'll use it is to kick off the application's main event loop (which you'll see later in this tutorial). The application is also the object responsible for managing "global" resources like timers and the FOX registry. It is a different approach from some other GUI toolkits for Ruby, where these kinds of global resources are accessed using module-level methods. As you continue to develop programs using FXRuby, you'll learn about other ways that the FXApp object is used.

The next step is to create an FXMainWindow instance to serve as the application's main window. If you've used Ruby/Tk before, this is similar to its TkRoot window:

require 'rubygems'
require_gem 'fxruby'

include Fox

theApp = FXApp.new

theMainWindow = FXMainWindow.new(theApp, "Hello")

Here, we pass theApp as the first argument to FXMainWindow.new to associate the new FXMainWindow instance with this FXApp. The second argument to FXMainWindow.new is a string that will be used for the main window's title.

So far, all we've done is instantiate the client-side objects. Unlike most other toolkits, FOX makes a distinction between client-side data (such as an FXMainWindow object) and server-side data (such as the X window associated with that Ruby object). To create the server-side objects associated with the already-constructed client-side objects, we call FXApp#create:

require 'rubygems'
require_gem 'fxruby'

include Fox

theApp = FXApp.new

theMainWindow = FXMainWindow.new(theApp, "Hello")

theApp.create

By default, all windows in FXRuby programs are invisible, so we need to call our main window's show instance method:

require 'rubygems'
require_gem 'fxruby'

include Fox

theApp = FXApp.new

theMainWindow = FXMainWindow.new(theApp, "Hello")
theApp.create

theMainWindow.show

The last step is to start the program's main loop by calling theApp's run instance method:

require 'rubygems'
require_gem 'fxruby'

include Fox

theApp = FXApp.new

theMainWindow = FXMainWindow.new(theApp, "Hello")
theApp.create

theMainWindow.show

theApp.run

The FXApp#run method doesn't return until the program exits. It is similar to the mainloop method used for Ruby/Tk and Ruby/GTK, and you can in fact use FXApp#mainloop as an alias for run if you prefer.

At this point, we have a working (if not very interesting) program that uses FXRuby. If you run it, you'll see something like this: