= volute

It could be a 'set event bus', or a 'business logic relocator'.

It can be used to implement toy state machines, or dumb rule systems.

See examples/ and specs/


== usage

  gem install volute


== example : equation

  # license is MIT

  $:.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))

  require 'volute'

  #
  # our class

  class Equation
    include Volute

    attr_accessor :km, :h, :kph

    def initialize
      @km = 1.0
      @h = 1.0
      @kph = 1.0
    end

    def inspect

      "#{@km} km, #{@h} h, #{@kph} kph"
    end
  end

  #
  # a volute triggered for any 'set' operation on an attribute of book

  volute Equation do

    # object.vset(:state, x)
    #   is equivalent to
    # object.instance_variable_set(:@state, x)

    volute :km do
      object.vset(:h, value / object.kph)
    end
    volute :h do
      object.vset(:kph, object.km / value)
    end
    volute :kph do
      object.vset(:h, object.km / value)
    end
  end

  #
  # trying

  e = Equation.new
  p e # => 1.0 km, 1.0 h, 1.0 kph

  e.kph = 10.0
  p e # => 1.0 km, 0.1 h, 10.0 kph

  e.km = 5.0
  p e # => 5.0 km, 0.5 h, 10.0 kph


== example : some kind of state-machine

  # license is MIT
  #
  # a state-machine-ish example, inspired by the example at
  # http://github.com/qoobaa/transitions

  $:.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))

  require 'volute'

  #
  # our class

  class Book
    include Volute

    attr_accessor :stock
    attr_accessor :discontinued

    attr_reader :state

    def initialize (stock)
      @stock = stock
      @discontinued = false
      @state = :in_stock
    end
  end

  #
  # a volute triggered for any 'set' operation on an attribute of book

  volute Book do

    # object.volute_do_set(:state, x)
    #   is equivalent to
    # object.instance_variable_set(:@state, x)

    if object.stock <= 0
      object.volute_do_set(
        :state, object.discontinued ? :discontinued : :out_of_stock)
    else
      object.volute_do_set(
        :state, :in_stock)
    end
  end

  #
  # trying

  emma = Book.new(10)

  emma.stock = 2
  p emma.state # => :in_stock

  emma.stock = 0
  p emma.state # => :out_of_stock

  emma.discontinued = true
  p emma.state # => :discontinued


== license

MIT, see LICENSE.txt