How to build a Twitter desktop client using JRuby + MonkeyBars. As demo’d at RubyManor

1. Monkeybars
in the manor

3. What do you think?
about
Java?

4. DIE, DIE DIE, DIE DIE, DIE
DIE, DIE
DIE, DIE DIE, DIE
DIE, DIE
DIE, DIE
DIE, DIE
DIE, DIE
DIE, DIE DIE, DIE
DIE, DIE

7. What do you think?
About
JRuby?

8. What do you think?
About
JRuby?
(it’s not so bad really)

9. Before...
JRuby Installed
Netbeans Downloaded
Gems

10. Before...
JRuby Installed
Netbeans Downloaded
Gems

11. Before...
JRuby Installed
Netbeans Downloaded
Gems

12. Before...
JRuby Installed
Netbeans Downloaded
Gems

13. Twitter Client
The Spec
•Login
•Report errors
•Display friend tweets
•Post tweets

14. Creating...
the app

15. Initial Setup
+ scaffolding
$> monkeybars projectname
$> cd projectname
$> rawr install
(choose option 2)
$> jruby -S rake generate ALL='src/login'

16. Install Gems
and freeze Gems
$> jruby -S gem install twitter
$> cd lib/ruby
$> jruby -S gem unpack twitter
$> jruby -S gem unpack hpricot

17. Skeleton App
will look something like this

18. Net Beans
New Project
1. Import Existing Java project with sources
2. Add JRuby complete library
3. Add Swing..
Net
Beans

19. Net Beans
New Project
1. Import Existing Java project with sources
2. Add JRuby complete library
3. Add Swing..
LIVE DEMO!
Net
Beans

20. Under the hood
Like Rails but not as you know it
M VC

21. Under the hood
Like Rails but not as you know it
M VC

22. username.text
View
password.text
login_button
username
Controller Model password

23. Sample Code
a quick look
controllers, models, views
event handling

24. Controller
class LoginController < ApplicationController
set_model 'LoginModel'
set_view 'LoginView'
set_close_action :exit
def login_button_action_performed
model, view_transfer = view_state
if @user = model.login(model.username, model.password)
TweetController.instance.setup(model)
TweetController.instance.open
close
else
transfer[:errors] = model.errors
signal(:login_failed)
end
end
end

25. Model
class LoginModel
attr_accessor :username, :password, :message, :errors, :user
def login(username, password)
begin
@user = Twitter::Base.new(username, password)
@user.timeline
self
rescue Twitter::CantConnect => e
@errors ||= []
@errors << $!.to_s
return false
end
end
end

26. View
class LoginView < ApplicationView
set_java_class 'login.LoginFrame'
map :view => quot;username.textquot;, :model => :username
map :view => quot;password.textquot;, :model => :password
define_signal :name => :login_failed, :handler => :login_failed
def login_failed(model, transfer)
message.text = transfer[:errors].to_s
end
nom
end
nom..

27. The App
pre alpha 0.333333333333

29. Result

30. Package
For cross platform distro
rawr install
Text
2: Keep the current Rakefile, and add the rawr content to the top.
http://rawr.rubyforge.org/

31. Package
Commands
For cross platform distro
Text
Remember to edit your
build_configuration.yaml 1st

32. Package
Sample Config
for RAWR to generate app
# Name of the created jar file
project_name: tweetobix
# Directory to create and place produced project files in
output_dir: package
----------<SNIP>----------------
# Individual files that should be loaded on the classpath
classpath_files:
- lib/java/jruby-complete.jar
- lib/java/swing-layout-1.0.3.jar
see build_configuration.yaml

33. Tricks
and tips

35. Why didn’t you
use the twitter4r gem
?

36. jruby --command gem install twitter4r
Building native extensions. This could take a while...
mypath/jruby-1.1.4/lib/ruby/1.8/mkmf.rb:7: JRuby does not
support native extensions. Check wiki.jruby.org for alternatives.
(NotImplementedError)
from mypath/jruby-1.1.4/lib/ruby/1.8/mkmf.rb:1:in `require'
from extconf.rb:1
ERROR: Error installing twitter4r:
ERROR: Failed to build gem native extension.
mypath/jruby-1.1.4/bin/jruby extconf.rb install twitter4r
Gem files will remain installed in /mypath/jruby-1.1.4/lib/ruby/
gems/1.8/gems/json-1.1.3 for inspection.
Results logged to mypath/jruby-1.1.4/lib/ruby/gems/1.8/gems/
json-1.1.3/ext/json/ext/parser/gem_make.out

37. Requiring Gems
Frozen
require 'manifest'
# Add vendored gems to load path and require them automatically
Dir[File.expand_path(File.dirname(__FILE__) + quot;/../lib/ruby/**quot;)].map
do |dir|
lib = quot;#{dir}/libquot;
lib = dir if lib =~ /.w+$/ #File.directory? is broken in current
JRuby for dirs inside jars
$: << lib
gem_name = File.basename(dir.gsub(/-d+.d+.d+$/, ''))
gem_path = dir + quot;/lib/quot; + gem_name + quot;.rbquot;
begin
require gem_path if File.exists? gem_path
rescue
p quot;could not load gem #{gem_path}quot;
end
end

38. Gotchas
a few
java.lang.NullPointerException: null
build paths
gems

39. -1’s
The not so good
bits
• Assumes knowledge of Java
• Quirky MVC
• Learning curve
• Early days...

41. +1’s
The good
bits
• GUI Builder (using Netbeans)
• Interface with mature Java libs
• It’s all Ruby!
• Cross platform distribution
• No platform dependancy on Ruby
• Cutting edge

43. Blinked?
Go here
http://tweetobix.com
Steps plus code to download

45. Fin.
martinbtt
http://www.beyondthetype.com