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title: Migrating to Ruby 1.9

Migrating to Ruby 1.9

Bruce Williams @ Scotland on Rails, Edinburgh, April 2008

(Adapted S6/S9 Version from Original Slide Deck)

About Bruce Williams

Perpetrator of much random Ruby hackery, language tourist

Rubyist since 2001 (Full-time since 2005)

Open source developer, contributer, technical editor, designer

Occasionally blogs at codefluency.com

Ruby 1.8 / Ruby 1.9

1.8

  • Stable.
  • The syntax and language features you know and probably love.
  • The performance profile you know and might hate a little.

1.9

  • Unstable, transitional.
  • Many new syntax and language features.
  • Better performance, especially for computationally intensive operations.

Installing Ruby 1.9

  • Get it from ruby-lang.org; by release or subversion
  • Use ./configure --prefix=/somewhere/nice to put it where you want it
  • Probably use --program-suffix=1.9, too

Ruby's Releases - From Toybox to Toolshed

Born in Japan (1995) -> Beyond Japan (2001) -> .. on Rails (2004) -> Expansion (2008)

(development 1.5)
1.6.0 '00
1.6.1 '01
1.6.2 '01
1.6.3 '01
1.6.4 '02
1.6.5 '02
1.6.7 '02
1.6.8 '03 (development 1.7 ongoing)
1.8.0 '04
1.8.1 '04
1.8.2 '05
1.8.3 '05
1.8.4 '06
1.8.5 '06
1.8.6 '07 (development 1.9 ongoing)

Standard Library

  • rubygems added (+ prelude & ruby --disable-gems)
  • rake added
  • json (pure, ext) added
  • FasterCSV replaced the previous csv
  • Also added: ripper, probeprofiler, securerandom, HMAC digests (some others moved)
  • Removed: soap, wsdl, base64 (use @@str.pack/unpack 'm*'), and some rarely used, old libraries

Parser/Syntax Changes

New Hash Literal

{a: "foo"}
# => {:a=>"foo"}

{a: "bar", :b => "baz"}
# => {:a=>"bar", :b=>"baz"}

New Proc Literal, Invocation

multiply_by_2 = ->(x) { x * 2 }
# => #<Proc:0x3c5a50>

multiply_by_2.(4)
# => 8

Parser/Syntax Changes Continued

Splat arguments before

names = %w(joe john bill)
[*names, 'jack']
# => ["joe", "john", "bill", "jack"]

Method Parameter ordering

def say(language=:english, text)
  puts Translator[language].translate(text)
end
say "hello"
# hello
say :spanish, "hello"
# hola

Migrating Risk Factors

  • Text processing
  • "Clever" assignment with blocks
  • Some Hash enumerations
  • Metaprogramming, code generation

Tests are Good

I was surprised at how much work my 11th hour integration of the FasterCSV code was. It was a pure Ruby library that really didn't do a lot of fancy tricks, but I had to track down about 20 little issues to get it running under Ruby 1.9. Thank goodness it had terrific test coverage to lead me to the problem areas.

-- James Edward Gray II (December 2007)

Follow-up Posting: Getting Code Ready for Ruby 1.9

Block Local Variables - Arguments Are Always Local

item = 1
2.upto(4) do |item|
  p item
end

Outputs In 1.8

# 2
# 3
# 4
item
# => 4

Outputs In 1.9

# 2
# 3
# 4
item
# => 1

Shadowing Variables - You'll Get a Warning

i = 1
lambda { |i| p i }.call(3)

Outputs In 1.8

# 3
i
# => 3

Outputs In 1.9

# 3
i
# => 1

warning line 2: shadowing outer local variable - i

Shadowing Variables - Locals, But Warned

No Local, Reassigns

d = 2
-> { d = 1 }.()
d
# => 1

Local, shadowed

d = 2
->(;d) { d = 1 }.()
d
# => 2

warning line 2: shadowing outer local variable - d

Hash#select - Changes to Yielded Arguments

Ruby 1.8

conferences.select do |data|
  p data
end
# [:euruko, "Prague"]
# [:scotland_on_rails, "Edinburgh"]
# [:railsconf_europe, "Berlin"]

warning: multiple values for a block parameter (2 for 1)

Ruby 1.9

conferences.select do |data|
  p data
end
# :euruko
# :scotland_on_rails
# :railsconf_europe

conferences.select do |name, city|
  p [name, city]
end
# [:euruko, "Prague"]
# [:scotland_on_rails, "Edinburgh"]
# [:railsconf_europe, "Berlin"]

Hash#select - Returns a Hash

conferences.select do |name, _|
  name == :scotland_on_rails
end

Ruby 1.8

# => [[:scotland_on_rails, "Edinburgh"]]

Ruby 1.9

# => {:scotland_on_rails=>"Edinburgh"}

Multilingualization (m17n)

  • There is one type of string, and the encoding is mutable
  • Strings are no longer Enumerable (use #each_char, #each_line, etc)
  • The encoding is 'lazy' and can be set by probing with String#ascii_only? and String#valid_encoding?.
  • Various ways to set default encoding (commandline, magic comments)
  • String#[] now returns a String, not a Fixnum (use ord)

Multilingualization (m17n) Continued

Encodings

:ASCII_8BIT, :Big5, :BIG5, :CP949, :EUC_JP, :EUC_KR, :EUC_TW, :GB18030, :GBK, :ISO_8859_1, :ISO_8859_2, :ISO_8859_3, :ISO_8859_4, :ISO_8859_5, :ISO_8859_6, :ISO_8859_7, :ISO_8859_8, :ISO_8859_9, :ISO_8859_10, :ISO_8859_11, :ISO_8859_13, :ISO_8859_14, :ISO_8859_15, :ISO_8859_16, :KOI8_R, :KOI8_U, :Shift_JIS, :SHIFT_JIS, :US_ASCII, :UTF_8, :UTF_16BE, :UTF_16LE, :UTF_32BE, :UTF_32LE, :Windows_1251, :WINDOWS_1251, :BINARY, :IBM437, :CP437, :IBM737, :CP737, :IBM775, :CP775, :CP850, :IBM850, :IBM852, :CP852, :IBM855, :CP855, :IBM857, :CP857, :IBM860, :CP860, :IBM861, :CP861, :IBM862, :CP862, :IBM863, :CP863, :IBM864, :CP864, :IBM865, :CP865, :IBM866, :CP866, :IBM869, :CP869, :Windows_1258, :WINDOWS_1258, :CP1258, :GB1988, :MacCentEuro, :MACCENTEURO, :MacCroatian, :MACCROATIAN, :MacCyrillic, :MACCYRILLIC, :MacGreek, :MACGREEK, :MacIceland, :MACICELAND, :MacRoman, :MACROMAN, :MacRomania, :MACROMANIA, :MacThai, :MACTHAI, :MacTurkish, :MACTURKISH, :MacUkraine, :MACUKRAINE, :CP950, :EucJP, :EUCJP, :EucJP_ms, :EUCJP_MS, :EUC_JP_MS, :CP51932, :EucKR, :EUCKR, :EucTW, :EUCTW, :EUC_CN, :EucCN, :EUCCN, :GB12345, :CP936, :ISO_2022_JP, :ISO2022_JP, :ISO_2022_JP_2, :ISO2022_JP2, :ISO8859_1, :Windows_1252, :WINDOWS_1252, :CP1252, :ISO8859_2, :Windows_1250, :WINDOWS_1250, :CP1250, :ISO8859_3, :ISO8859_4, :ISO8859_5, :ISO8859_6, :Windows_1256, :WINDOWS_1256, :CP1256, :ISO8859_7, :Windows_1253, :WINDOWS_1253, :CP1253, :ISO8859_8, :Windows_1255, :WINDOWS_1255, :CP1255, :ISO8859_9, :Windows_1254, :WINDOWS_1254, :CP1254, :ISO8859_10, :ISO8859_11, :TIS_620, :Windows_874, :WINDOWS_874, :CP874, :ISO8859_13, :Windows_1257, :WINDOWS_1257, :CP1257, :ISO8859_14, :ISO8859_15, :ISO8859_16, :CP878, :SJIS, :Windows_31J, :WINDOWS_31J, :CP932, :CsWindows31J, :CSWINDOWS31J, :MacJapanese, :MACJAPANESE, :MacJapan, :MACJAPAN, :ASCII, :ANSI_X3_4_1968, :UTF_7, :CP65000, :CP65001, :UCS_2BE, :UCS_4BE, :UCS_4LE, :CP1251

Multilingualization (m17n) Continued

Read a file with File.read

File.read("input.txt").encoding
# => #<Encoding:UTF-8>

File.read("input.txt", encoding: 'ascii-8bit').encoding
# => #<Encoding:ASCII-8BIT>

Read a file with File.open

result = File.open("input.txt", "r:euc-jp") do |f|
  f.read
end
result.encoding
# => #<Encoding:EUC-JP>
result.valid_encoding?
# => true

Regular Expressions - Oniguruma Engine

  • Same basic API
  • Much Better performance
  • Support for encodings
  • Extended Syntax
    • Look-ahead (?=), (?!), look-behind (?<), (?<!)
    • Named groups (?<>), backreferences, etc

Named Groups

"His name is Joe".match(/name is (?<name>\S+)/)[:name]
# => "Joe"

Enumerable

Enumerator built-in, returned from Enumerable methods (and those in Array, Dir, Hash, IO, Range, String or Struct that serve the same purposes). Added Enumerator#with_index

Map with Index

%w(Joe John Jack).map.with_index do |name, offset|
  "#{name} is #{offset + 1}"
end
# => ["Joe is #1", "John is #2", "Jack is #3"]

Enumerable - Reduce (inject)

[1,2,3,4].reduce(:+)
# => 10

Enumerable Continued

New Enumerable methods take, group_by, drop, min_by, max_by, count, and others. Enumerable#inject/reduce can take a single argument.

take

array = [1, 2, 3, 4, 5]
array.take(3)
# => [1, 2, 3]
array
# => [1, 2, 3, 4, 5]

drop

array = [1, 2, 3, 4, 5]
array.drop(3)
# => [4, 5]
array
# => [1, 2, 3, 4, 5]

Hash Changes - Insertion Order Preserved

conferences = {
  euruko: 'Prague',
  scotland_on_rails: 'Edinburgh'
}
conferences[:railsconf_europe] = 'Berlin'
conferences.each do |name, city|
  p "#{name} is in #{city}"
end

# "euruko is in Prague"
# "scotland_on_rails is in Edinburgh"
# "railsconf_europe is in Berlin"

conferences.delete(:scotland_on_rails)
conferences[:scotland_on_rails] = 'Edinburgh'
conferences.each do |name, city|
  p "#{name} is in #{city}"
end

# "euruko is in Prague"
# "railsconf_europe is in Berlin"
# "scotland_on_rails is in Edinburgh"

Object - Added tap

thing = Thing.new.tap do |thing|
  thing.something = 1
  thing.something_else = 2
end

Lambda Changes - Obfuscation, Ahoy!

  • New literal syntax more flexible
  • Not possible in { | | ... } style literals

Passing Blocks

m = ->(x, &b) { b.(x * 2) if b }
m.(3) do |result|
  puts result
end
# Output
# 6

Default Arguments

->(a, b=2) { a * b }.(3)
# => 6

Symbol Changes - Less Sibling Rivalry

  • Added to_proc
  • Added =~, [] like String (to_s less needed), sortable
  • Object#methods, etc now return an array of symbols

Indexing into a Symbol

:foo[1]
# => "o"

Comparing with a String

:this === "this"
# => true

Fibers - "Semi-Coroutines"

  • Similar to Python's generators
  • Owe method naming lineage to Lua
  • Out of scope of the talk, but very cool

For some examples, see:

Thanks!

This was really just an introduction.

Bruce Williams // bruce AT codefluency.com // twitter: wbruce