Example of the quiescent gem

foo.rb

require 'quiescent'

class Foo
  include Quiescent

  # This declares a constant named PostCode that 
  # quiesces to a default value of 53706 unless 
  # another is provided before the first time it
  # is read
  quiescent :PostCode, 53706

  # Let's assume that the awesome features are off
  # by default.
  quiescent :EnableTotallyAwesomeFeature, false
  quiescent :EnableSlightlyLessAwesomeFeature, false

  # This declares a constant named LazyThrees that 
  # quiesces to a list of all natural numbers less than
  # 100 that are divisible by three, as calculated
  # in the block, unless another value is provided. 
  # The block argument will execute at most once.
  quiescent :LazyThrees do
    (1..100).to_a.select {|x| x % 3 == 0}
  end

  # In this method, we'll see how to force quiescents
  # to quiesce by giving them values and reading their
  # values.
  def self.setup
    # We only want to do this once
    return if @setup_done
    @setup_done = true

    puts "The postal code is #{Foo::PostCode}"

    # You can provide non-default values with the
    # quiesce method...
    Foo.quiesce(:EnableTotallyAwesomeFeature, "sometimes")

    # ...or by using a special CONSTNAME= method, which
    # will be intercepted by method_missing.
    Foo.EnableSlightlyLessAwesomeFeature = true

    # Note that this only works for names corresponding
    # to declared quiescing constants...
    begin
      Foo.EnableCrummyFeature = true 
    rescue Exception
      puts("whoa, failure in aisle 47")
    end

    # ...and only once for each quiescing constant.
    begin
      Foo.EnableSlightlyLessAwesomeFeature = false
    rescue Exception
      puts("nice try, pal")
    end
  end
end