visualruby

This "hello world" script is simple, but there are some important lessons to be learned from it.

As before, the HelloGUI.rb class has a corresponding glade file, HelloGUI.glade, to add a GUI. It maps like this:

HelloGUI.rb ==> glade/HelloGUI.glade

If you doubleclick on HelloGUI.glade, the file will open, and you can see the button with ID: "ui_hello_btn"

This ID follows a naming convention:

ui = user interface hello = identifier btn = a button

This naming convention isn't required, but it helps distinguish a variable that refers to a widget from one of your variables.

The main program creates an instance of the HelloGUI class and shows it:

HelloGUI.new().show_glade()

The following method uses this ID, such that it runs when the button is clicked:

From HelloGUI.rb:

def ui_hello_btn__clicked(*args) alert("Hello World") end

The name of this method is definately not an accident. It follows a naming convention:

__ # two underscores between ID and event!

So the method, ui_hello_btn__clicked(*args) runs when the button with glade ID "ui_hello_btn" encounters a "clicked" event. To make this work, you only need to create a unique glade ID and name your method correctly. It will call the method based on its name.

SUMMARY:

• Give the widgets on the form unique glade IDs, then refer to them by their ID.
• Store your glade files in the subdirectory /glade. Mapping: MyClass.rb => glade/MyClass.glade
• Visualruby will call event handlers by the naming convention: __ (see next examples)