Brony User Group Cologne hosted by 18.7.2012 

Ruby #138 Spectacular 

“Hold on to your hooves, I'm about to be BRILLIANT!” – Pinkie Pie 

undef_method 

Configuration DSL App.configure do |config| redis do host "127.0.0.1" port 6379 end amqp do host "127.0.0.1" port 5672 auto_recovery true timeout 1 logging true end end 

ArgumentError: wrong number of arguments (0 for 1) ! from …/lib/ruby/1.9.1/timeout.rb:98:in `timeout' ! from … App.config[:amqp][:timeout] 

What in tarnation?! 

# File: timeout.rb module Timeout def timeout(sec, klass = nil) #:yield: +sec+ # Implementation of the timeout functionality end module_function :timeout end # Identical to: # # Timeout::timeout(n, e, &block). # # This method is deprecated and provided only for backwards compatibility. # You should use Timeout#timeout instead. def timeout(n, e = nil, &block) Timeout::timeout(n, e, &block) end Global Namespace Pollution! 

class App class Configuration < Hash undef_method(:timeout) def initialize(&block) super() instance_eval &block end def method_missing(meth, *subjects, &block) # Fancy method_missing action for DSL end end def self.configure(&block) @config = App::Configuration.new(block) end end 

App.config[:amqp][:timeout] # => 1 

method(:method_name) 

Callbacks bei asynchroner Ausführung class AmqpClient def connect(options = {}) @connection = AMQP.connect(options) { |connection| … } @connection.on_tcp_connection_loss do |connection, settings| # Handle connection loss end @connection.on_recovery do |connection, settings| # Handle connection recovery end end def publish(message); end end 

Probleme? Callbacks in Blockform sind sehr schwer zu testen Sehr große initialize-Methode Dokumentation der Callbacks umständlich Callbacks nur implizit 

method to the rescue 

class AmqpClient def connect(options = {}) @connection.on_tcp_connection_loss &method(:on_tcp_connection_loss) @connection.on_recovery &method(:on_recovery) end def on_tcp_connection_loss(connection, settings) # Handle connection loss end def on_recovery(connection, settings) # Handle connection recovery end end 

Callbacks einzeln und in Isolation testbar initialize-Method übersichtlicher Dokumentation der Callbacks über RDoc etc. möglich Callbacks sind explizit gemacht 

Ruby is Magic ist nicht immer sinnlos In manchen Fällen kann es Code verbessern Immer abzuwägen wie viele und wer den Code noch lesen muss 

One More Thing … 

No content

Binding 

Kapseln den Ausführungskontext Erhalten Zugriff auf Variablen, Methoden, self Werden erzeugt mit Kernel#binding 

class Pony def say_hello(a_binding = nil) eval('puts "Hello, my name is #{@name}"', a_binding || binding) end end somepony = Pony.new somepony.say_hello # Hello, my name is @name = "Rainbow Dash" somepony.say_hello(binding) # Hello, my name is Rainbow Dash @name = "Applejack" somepony.say_hello(binding) # Hello, my name is Applejack 

Okay … 

… ERB! 

require 'erb' class View def friend "Pinkie Pie" end def get_binding binding end end template = ERB.new <<-ERB Welcome to Ruby is Magic! Let me introduce you to my good friend <%= friend %>. ERB puts template.result # (erb):3:in `': undefined local variable or method `friend' for main:Object # from /lib/ruby/1.9.1/erb.rb:838:in `eval' # from /lib/ruby/1.9.1/erb.rb:838:in `result' # from Ruby is Magic.rb/011-clip-show/code/erb_demo.rb:19:in `' puts template.result(View.new.get_binding) # Let me introduce you to my good friend Pinkie Pie. 

Giveaway 

autocmd FileType ruby compiler ruby function Run() let executable=b:current_compiler if !getbufvar("%", "&saved") let tmpfile = tempname() silent! exe "write " . tmpfile . ".rb" endif let filename=expand('%:p') " Create the previewwindow if doesn't exist if ! &previewwindow pedit /tmp/_vim_previewwindow endif " Change to the previewwindow silent! wincmd P " Run the file with and switch back to the previous window execute "%d|silent 0r!" . executable . " '" . filename . "'" wincmd p endfunction map r :call Run() 

https://gist.github.com/3137064 

Thanks! Q & A? Dirk Breuer / @railsbros_dirk Sebastian Cohnen / @tisba ? “My Little Pony” © Hasbro Studios and DHX Media Vancouver rubyismagic.de