Ruby language overview & new features of 2.0 release - talk presented at #64 Java User Group meeting on march 2, 2013

1. happy 20th birthday!
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2. Yukihiro Matsumoto
matz
osaka
april 14, 1965
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3. “I always thought Smalltalk would beat Java.I just didn’t
know if would be called ‘Ruby’ when it did so”
- Kent Beck -
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4. The Ruby Language
• Designed for programmer productivity and fun
• Generic, interpreted, reflective, with garbage collection
• Optimized for people rather than computers
• More powerful than Perl, more object oriented than Python
• Everything is an object. There are no primitive types
• Strong dynamic typing
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5. implementations
• Matz's Ruby Interpreter or MRI, uses its own Ruby-specific virtual machine
written in C
• JRuby, runs on the Java virtual machine
• Rubinius, C++ bytecode VM that uses LLVM to compile to machine code at
runtime
• MagLev, a Smalltalk implementation
• MacRuby, an OS X implementation on the Objective-C runtime
• IronRuby, an implementation on the .NET Framework
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6. versions
v0.95 - December 21, 1995
v1.0 - December 25, 1996
v1.2 - December 1998
v1.3 - year1999
v1.4 - August 1999
v1.6 - September 2000
v1.8 - August 2003
Ruby on Rails - 2005
v1.9 - December 2007
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7. Everything in Ruby is
‣ Assignment - binding names to objects
‣ Control structures - if/else, while, case
‣ Sending messages to objects - methods
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8. irb
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9. strings
a = "nThis is a double-quoted stringn"
a = %Q{nThis is a double-quoted stringn}
a = %{nThis is a double-quoted stringn}
a = %/nThis is a double-quoted stringn/
a = <<-BLOCK
This is a double-quoted string
BLOCK
a = 'This is a single-quoted string'
a = %q{This is a single-quoted string}
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10. collections
a = [1, 'hi', 3.14, 1, 2, [4, 5]]
puts a[2] # 3.14
puts a.[](2) # 3.14
puts a.reverse # [[4, 5], 2, 1, 3.14, 'hi', 1]
puts a.flatten.uniq # [1, 'hi', 3.14, 2, 4, 5]
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11. associative arrays
hash = Hash.new
hash = { :water => 'wet', :fire => 'hot' }
puts hash[:fire]
# => hot
hash.each do |key, value|
puts "#{key} is #{value}"
end
# => water is wet
# fire is hot
hash.delete :water
# Deletes water: 'wet'
hash.delete_if { |key,value| value == 'hot'}
# Deletes :fire => 'hot'
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12. blocks & iterators
do
puts "Hello, World!"
end
oppure
{ puts "Hello, World!" }
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13. closures
# In an object instance variable (denoted with '@'),
remember a block.
def remember(&a_block)
@block = a_block
end
# Invoke the above method, giving it a block which takes a
name.
remember {|name| puts "Hello, #{name}!"}
# When the time is right (for the object) -- call the
closure!
@block.call("Jon")
# => "Hello, Jon!"
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14. closures
def create_set_and_get(initial_value=0) # Note the default value of 0
closure_value = initial_value
return Proc.new {|x| closure_value = x}, Proc.new { closure_value }
end
setter, getter = create_set_and_get # ie. returns two values
setter.call(21)
getter.call # => 21
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15. closures
def create_set_and_get(initial_value=0) # Note the default value of 0
closure_value = initial_value
return Proc.new {|x| closure_value = x}, Proc.new { closure_value }
end
setter, getter = create_set_and_get # ie. returns two values
setter.call(21)
getter.call # => 21
#You can also use a parameter variable as a binding for the closure.
#So the above can be rewritten as...
def create_set_and_get(closure_value=0)
return proc {|x| closure_value = x } , proc { closure_value }
en
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16. yield
def use_hello
yield "hello"
end
# Invoke the above method, passing it a block.
use_hello {|string| puts string} # => 'hello'
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17. enumeration
array = [1, 'hi', 3.14]
array.each {|item| puts item }
# => 1
# => 'hi'
# => 3.14
array.each_index do|index|
puts "#{index}: #{array[index]}"
end
# => 0: 1
# => 1: 'hi'
# => 2: 3.14
# The following uses a Range
(3..6).each {|num| puts num }
# => 3
# => 4
# => 5
# => 6
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18. functional programming
[1,3,5].inject(10) {|sum, element| sum + element}
# => 19
File.open('file.txt', 'w') do |file|
# 'w' denotes "write mode"
file.puts 'Wrote some text.'
end # File is automatically closed here
File.readlines('file.txt').each do |line|
puts line
end
(1..10).collect {|x| x*x}
# => [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
(1..5).collect(&:to_f)
# => [1.0, 2.0, 3.0, 4.0, 5.0]
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19. classes
class Person
attr_reader :name, :age
def initialize(name, age)
@name, @age = name, age
end
def <=>(person) # Comparison operator for sorting
age <=> person.age
end
def to_s
"#{name} (#{age})"
end
end
group = [
Person.new("Bob", 33),
Person.new("Chris", 16),
Person.new("Ash", 23)
]
puts group.sort.reverse
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20. monkey patching
# re-open Ruby's Time class
class Time
def yesterday
self - 86400
end
end
today = Time.now
# => Thu Aug 14 16:51:50 +1200 2012
yesterday = today.yesterday
# => Wed Aug 13 16:51:50 +1200 2012
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21. metaprogramming
COLORS = { black: "000",
red: "f00",
green: "0f0",
yellow: "ff0",
blue: "00f",
magenta: "f0f",
cyan: "0ff",
white: "fff" }
class String
COLORS.each do |color,code|
define_method "in_#{color}" do
"<span style="color: ##{code}">#{self}</span>"
end
end
end
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22. 2.0
fully backward compatible with Ruby 1.9.3
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23. default source encoding is UTF-8
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24. require improvements
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25. GC is copy-on-write friendly
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26. Fine-Grained Asynchronous
Interrupt Handling
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27. D-Trace support
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28. keyword arguments
def render(source, opts = {})
opts = {fmt: 'html'}.merge(opts)
r = Renderer.for(opts[:fmt])
1.9 r.render(source)
end
render(template, fmt: 'json')
def render(source, fmt: 'html')
r = Renderer.for(fmt)
r.render(source)
2.0 end
render(template, fmt: 'json')
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29. 1.9
problems are on method definition
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30. Caller side doesn't change
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31. lazy enumerables
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32. lazy enumerables
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33. lazy enumerables
def natural_numbers
(1..Float::INFINITY).lazy
end
def primes
natural_numbers.select {|n|
(2..(n**0.5)).all? {|f|
n % f > 0
}
}
end
primes.take(10).force
#=> [1, 2, 3, 5, 7, 11, 13, 17, 19, 23]
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34. Module Prepending
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35. Module Prepending
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36. Module Prepending
no more alias method chain
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37. :ruby and so.why?(‘not’)
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38. :ruby and so.why?(‘not’)
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39. http://www.ruby-lang.org/
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40. http://www.ruby-doc.org/
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41. http://modulecounts.com/
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42. http://www.rubygems.org/
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43. seesaw
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44. questions?
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45. !anks.
@fuzziness
michele@franzin.net
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46. http://en.wikipedia.org/wiki/Ruby_(programming_language)
credits
http://benhoskin.gs/2013/02/24/ruby-2-0-by-example
http://benhoskin.gs/2013/02/24/getting-to-know-ruby-2-0
https://speakerdeck.com/shyouhei/whats-new-in-ruby-2-dot-0
http://www.slideshare.net/peter_marklund/ruby-on-rails-101-presentation-slides-
for-a-five-day-introductory-course
lunedì 4 marzo 13