Question

I have a function that presents the user a combo-box.

def select_interface(interfaces)   list_box :items => interfaces do |list|     interface = list.text   end   ### ideally should wait until interface has a value then: ###   return interface end 

The rest of the program depends on the selection from this combo-box.

I would like to find a way to make ruby wait for the input from the combo-box and then carry executing the rest of the code.

There is a similar function in shoes called ask that will wait for the input of the user.

interface =  ask('write your interface here') 

How can I implement this ‘wait until the variable has a value’ function in Ruby/shoes?

Answer 1

It took me a while to understand your question 🙂 I started writing a long answer about the entire theory of GUI applications. But you already have everything you need. The block that list_box takes is really its change method. You’re telling it what to do when it gets changed. Just defer the rest of the program to run when you get a value you want.

Shoes.app do    interfaces = ['blah', 'blah1', 'blah2']   # proc is also called lambda   @run_rest_of_application = proc do     if @interface == 'blah'       do_blah     # etc   end    @list_box = list_box(:items => interfaces) do |list|     @interface = list.text     @run_rest_of_application.call     @list_box.hide # Maybe you only wanted this one time?   end end 

This is the basic idea behind all GUI applications: build the initial application then wait for ‘events’, which will create new states for you respond to. In ruby-gnome2, for example, you would use a callback function/block with a Gtk::ComboBox that would change the state of your application. Something like this:

# Let's say you're in a method in a class @interface = nil @combobox.signal_connect('changed') do |widget|    @interface = widget.selection.selected   rebuild_using_interface end 

Even outside of a toolkit you can get a ‘free’ events system using Ruby’s Observer module. Hope this helped.