Ruby for desktop applications? Yes we can.

http://fletcherm.github.com/gr_jug_2011

(credit Mike Karlesky)

DOS simulators => Java + JRuby simulators

Demos!

Techs

Java

(we all know what that is)

JRuby

Ruby interpreter on the JVM

Production Simulator - JRuby 1.0 (2007)

Write Ruby

class ConfigurationFacade
  def initialize
    @config = ...
  end

  def method_missing(name, *args, &block)
    @config[name.to_s]
  end

  def capital_investment
    @config["capital_investment"].present?
      ? @config["capital_investment"]
      : 0
  end
end

Interface with Java

class AgingReportView
  def view(parent)
    @table_model = ReadOnlyTableModel.new
    @aging = JTable.new(@table_model)
    @aging.row_selection_allowed = false
    @aging.cell_selection_enabled = true
  end
end

Cross-pollinate for maximum goodness

def invoke_later(&block)
  if javax.swing.SwingUtilities.
                 is_event_dispatch_thread
    block.call
  else
    ...
  end
end

SwingUtilities.invoke_later(Runnable.impl do
  begin
    block.call
  rescue Exception => ex
    puts ex.message
    puts ex.backtrace.join("\n")
  end
end)

def add_row(row)
  invoke_later do
    @table_model.add_row row.to_java
  end
end

def clear_rows
  invoke_later do
    @table_model.clear
  end
end

RSpec for testing

2120 unit tests

286 system tests

Substance - look and feel

Apache Batik - SVG

Java scenegraph

JFreeChart

Beta distribution

Bouncy Castle - encryption

YAML - configuration

NSIS - Windows installer

Launch4J - Windows Java app launcher

.app bundle on Mac

shell script on Linux

Development

Presenter First

Write Presenter tests first to define view & model behavior

Just say 'When'

class PlayPresenter
  constructor :model, :view

  def setup
    @view.when :pause_clicked do
      @model.pause
      @view.hide_play
      @view.show_pause
    end

    @view.when :play_clicked do
      if @model.paused?
        @model.resume
      else
        @model.play
      end
    end
  end
end

describe Ui::PlayPresenter do
  before do
    create_mocks(:view, :model)

    @play = @view.trap.when :play_clicked
    @pause = @view.trap.when :pause_clicked

    Ui::PlayPresenter.new(@model, @view)
  end
end

it 'pauses the sim when Pause is clicked' do
  @model.expects.pause
  @view.expects.hide_play
  @view.expects.show_pause

  @pause.trigger

  verify_mocks
end

it 'starts the sim when Play is clicked' do
  @model.expects.paused?.returns false
  @model.expects.play

  @play.trigger

  verify_mocks
end

it 'resumes the sim when Play
    is clicked after a Pause' do
  @model.expects.paused?.returns true
  @model.expects.resume

  @play.trigger

  verify_mocks
end

class PlayPresenter
  constructor :model, :view

  def setup
    @view.when :pause_clicked do
      @model.pause
      @view.hide_play
      @view.show_pause
    end

    @view.when :play_clicked do
      if @model.paused?
        @model.resume
      else
        @model.play
      end
    end
  end
end

Presenters tend to have simple, targetted tests and behavior

Heavier behavior defined in models

Views are thin walls around untestable code

26, 29 MVP triples in each app