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What I Love About Ruby

What I Love About Ruby

An introduction to some of the coolest features of the Ruby language.

keithrbennett

May 12, 2012
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  1. 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

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  2. 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...

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  3. 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?

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  4. 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.

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  5. 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

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  6. 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!”

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  7. 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

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  8. 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

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  9. 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

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  10. 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)}.
    """

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  11. Keith Bennett
    keithrbennett at gmail dot com
    What I Love About Ruby
    19 February 2010
    Asian Institute of Technology
    Bangkok, Thailand
    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

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  12. Keith Bennett
    keithrbennett at gmail dot com
    What I Love About Ruby
    19 February 2010
    Asian Institute of Technology
    Bangkok, Thailand
    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

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  13. 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.

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  14. 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!

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  15. 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

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  16. 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

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  17. Keith Bennett
    keithrbennett at gmail dot com
    What I Love About Ruby
    19 February 2010
    Asian Institute of Technology
    Bangkok, Thailand
    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]

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  18. 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.

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  19. 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"]

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  20. 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

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  21. 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

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  22. 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'.

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  23. 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.

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  24. 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

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  25. 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 }

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  26. 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.”

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  27. Keith Bennett
    keithrbennett at gmail dot com
    What I Love About Ruby
    19 February 2010
    Asian Institute of Technology
    Bangkok, Thailand
    The End

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