Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Who I Am ● Keith Bennett, keithrbennett at gmail.com ● Software Developer living near Washington, DC, USA ● Original hometown is New York City ● 25+ years experience, focusing on Ruby and Java, currently studying Android development ● Technical Interests: Ruby, Android, Clojure ● Other Interests: Travel, Music, Study of Massage and Asian and European Languages
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Obligatory Joke, Part 1 A DBA walks into a bar, steps in front of two tables and says...
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Obligatory Joke, Part 2 ...may I join you?
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Please... ● ...ask me to slow down if I speak too quickly. ● ...ask me again if I forget. ● ...ask questions if anything I say is not clear. ● ...feel free to share your own observations and experiences.
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand What I Love About Ruby: Overview ● Conciseness and Clarity, Not Ceremony (high signal to noise ratio) ● Expressive Syntax ● Powerful Enumerable Processing ● Code Blocks and Closures ● Everything’s an Object, even 1 and nil ● Ranges ● Regular Expressions ● JRuby ● IRB ● OS Scripting Support ● Metaprogramming
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Conciseness and Clarity, Not Ceremony: Main Program ● Java: public class HelloWorld { public static void main(String args) { System.out.println("Hello world!"); } } ● Ruby: puts “Hello world!”
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Conciseness and Clarity, Not Ceremony: Instance Variable Access ● Java: private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } ● Ruby: attr_accessor :name
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Conciseness and Clarity, Not Ceremony: List/Array Subtraction ● Java: public static List subtractList(List minuendList, List subtrahendList) { List differenceList = new ArrayList(); for (Object o : minuendList) { if (! subtrahendList.contains(o)) { differenceList.add(o); } } return differenceList; } ● Ruby minuendList – subtrahendList
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Conciseness and Clarity, Not Ceremony: List Manipulation ● Java: public static List calcDoubles(List inputList) { List outputList = new ArrayList(); for (Integer n : inputList) { outputList.add(2 * n); } return outputList; } ● Ruby: def calc_doubles(input_list) input_list.map { |n| 2 * n } end
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Conciseness and Clarity, Not Ceremony: Multiline Strings """ Dear #{customer_name}, Thank you for your purchase on #{formatAsDate(purchase_date)}. We have billed your credit card for #{formatAsMoney(purchase_amount)}. """
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Code Block Function Parameters ● Functions can have code blocks passed to them as the last argument without explicitly declaring them. ● Inside the function, block_given? Can be called to determine the presence/absence of the block. irb(main):001:0> def foo irb(main):002:1> if block_given? ; yield; else; puts "No block given."; end irb(main):003:1> end irb(main):005:0* foo { puts "I'm passing a block." } I'm passing a block. irb(main):006:0> foo No block given.
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Closures ● The puts function is passed the closure (underlined), and has access to the variable name even though name is not in its scope. This makes the code block a closure. irb(main):008:0> name = 'Joe' => "Joe" irb(main):009:0> 3.times { puts "Hi, #{name}! " } Hi, Joe! Hi, Joe! Hi, Joe!
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Automatic Cleanup or State Restoration Using Closures File.open('myfile.txt') do |file| file << 'hi' # do something with the file end # the file is automatically closed Dir.chdir('another/dir') do # do something in that directory end # chdir's back to the original directory
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Everything’s an Object, Even 1 and nil irb(main):020:0> 1.class => Fixnum irb(main):021:0> [].class => Array irb(main):022:0> {}.class => Hash irb(main):023:0> //.class => Regexp irb(main):024:0> self.class => Object irb(main):025:0> nil.class => NilClass irb(main):001:0> (0..10).class => Range
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Regular Expressions ● Can be used as a literal, i.e. without a reference: /^A/ ● =~ returns an index (or nil if not found). ● === returns a boolean value representing the presence or absence of a match. ● Can be used in a case statement, and can simulate multimethods in this way.
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Regular Expression Literals irb(main):001:0> fruits = %w(apple mango peach pear) => ["apple", "mango", "peach", "pear"] irb(main):002:0> fruits.grep /^p/ => ["peach", "pear"] irb(main):003:0> p_regex = /^p/; fruits.grep p_regex => ["peach", "pear"]
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Regular Expression Presence/Absence Using === irb(main):005:0> /^p/ === 'peach' => true irb(main):006:0> /^p/ === 'mango' => false
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Regular Expression Position Using =~ irb(main):007:0> 'peach' =~ /c/ => 3 irb(main):008:0> 'mango' =~ /c/ => nil
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Regular Expressions in Case Statements irb(main):013:0> def test_for_a(word) irb(main):014:1> case word irb(main):015:2> when /^a/ irb(main):016:2> puts "#{word} begins with an 'a'." irb(main):017:2> else irb(main):018:2* puts "#{word} does *not* begin with an 'a'." irb(main):019:2> end irb(main):020:1> end irb(main):021:0> irb(main):022:0* test_for_a('mango') mango does *not* begin with an 'a'. irb(main):023:0> test_for_a('apple') apple begins with an 'a'.
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand JRuby ● Runs in the Java Virtual Machine. ● Leverages existing Java libraries and infrastructure. ● Can be a better Java than Java (e.g. provides irb interactive shell). ● Unit testing Java code with JRuby (e.g. with rspec) is more flexible and expressive than testing in JUnit. ● JRuby can be used to script DB access via JDBC. ● jruby-complete.jar contains Jruby and gem, irb, rake, rdoc, ri utilities.
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand JRuby as a Java Shell ● Get available locales: import 'java.util.Locale' Locale.available_locales.each do |locale| puts locale.display_name end ● Show “os.” System Properties import java.lang.System os_properties = System.properties.select do |key, value| /^os./ === key end
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Operating System Scripting ● Ruby’s power and expressiveness can be combined with OS resources and commands: `find . -name \"*.tmp\" -exec rm {} \";\"` ● However, Ruby has its own functions that can substitute for OS commands, enabling scripting that's OS-neutral and easier to read: Dir.glob('**/*.tmp').each { |f| File.delete f }
Keith Bennett keithrbennett at gmail dot com What I Love About Ruby 19 February 2010 Asian Institute of Technology Bangkok, Thailand Metaprogramming ● Enables creation of DSL’s (Domain Specific Languages) such as Ruby on Rails ● Enables dramatic simplifications, such as attr_accessor ● Enables on-the-fly method creation, such as creating accessor methods on elements in a parsed XML file. ● The metaprogrammer’s t-shirt says: “I write code that writes code for food.”
keithrbennett
mode86
spinscale
iwamot
takahana
ymty
soracom
sakiengineer
taishin
gotok365
tkmnzm
devops_vtj
yoyakoba
sonatard
bkeepers
danielanewman
maggiecrowley
andyhume
lara
eileencodes
bermonpainter
keathley
addyosmani
colly
csswizardry