glimmer_listbox_multiple_selection.rb

class Person 
  attr_accessor :provinces, :provinces_options
  
  def initialize
    self.provinces_options=[
      "", 
      "Quebec", 
      "Ontario", 
      "Manitoba", 
      "Saskatchewan", 
      "Alberta", 
      "British Columbia", 
      "Nova Skotia", 
      "Newfoundland"
    ]
    self.provinces = ["Quebec", "Manitoba", "Alberta"]
  end
end

class HelloMultiSelectList
  include Glimmer
  def launch
    shell {
      list(multi) {
        selection bind(Person.new, :provinces)
      }
    }.open
  end
end

HelloMultiSelectList.new.launch