What I Love About Ruby

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

Obligatory Joke, Part 1 A DBA walks into a bar, steps in front of two tables and says...

Obligatory Joke, Part 2
...may I join you?

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.

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

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!”

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

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

Conciseness and Clarity, Not Ceremony: List Manipulation
Java:
public static List<Integer> calcDoubles(List<Integer> inputList) { List<Integer> outputList = new ArrayList<Integer>(); for (Integer n : inputList) { outputList.add(2 * n); } return outputList; }
Ruby:
def calc_doubles(input_list) input_list.map { |n| 2 * n } end

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)}. """

Expressive Syntax
3.times { puts “I love Ruby! “ }
stooges = ["Moe", "Larry", "Curly"] # or
stooges = %w(Moe Larry Curly)
country_codes = { 'Thailand' => 'th', 'Singapore' => 'sg' }
['mango', 'pineapple', 'durian'][-1] # “durian”
['mango', 'pineapple', 'durian'].last # “durian”
attr_accessor :id, :name
1_234_567 # 1234567

Powerful Enumerable Processing irb(main):001:0> nums = (1..12).to_a => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] irb(main):002:0> squares = nums.map { |n| n * n } => [1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144] irb(main):003:0> evens = nums.select { |n| n % 2 == 0 } => [2, 4, 6, 8, 10, 12] irb(main):004:0> odds = nums - evens => [1, 3, 5, 7, 9, 11] irb(main):005:0> sum = nums.inject { |sum,n| sum += n } => 78

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.

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!

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

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

Ranges irb(main):004:0> (0..3).class => Range irb(main):005:0> (0..3).to_a => [0, 1, 2, 3] irb(main):006:0> (0...3).to_a => [0, 1, 2] irb(main):007:0> nums = (0..10).to_a => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] irb(main):008:0> nums[3..5] => [3, 4, 5]

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.

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"]

Regular Expression Presence/Absence Using === irb(main):005:0> /^p/ === 'peach' => true irb(main):006:0> /^p/ === 'mango' => false

Regular Expression Position Using =~ irb(main):007:0> 'peach' =~ /c/ => 3 irb(main):008:0> 'mango' =~ /c/ => nil

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'.

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.

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

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 }

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.”

The End

What I Love About Ruby

by Keith Bennett on Feb 17, 2010

Accessibility

Categories

Tags

Upload Details

Usage Rights

2 Embeds 7

Statistics

What I Love About Ruby — Presentation Transcript

http://www.iaeronz.com	6
http://www.lmodules.com	1