$ ruby hello.rb
Hello, world!
$ 

$ irb
irb(main):001:0> puts "Hello, world!"
Hello, world!
=> nil
irb(main):002:0> exit 
$ 

puts "Hello, world!" 

メソッドの呼び出し

[object.]method([param[, ...]])

inp = gets
puts inp

行の継続

inp = gets; puts inp

puts(
  gets
  )

puts \
  gets

print "Which city do you like to visit? Paris, London or Rome? "
city = gets.chomp.upcase
if city == "PARIS"
  puts "Visit Le Musee de Louvre."
elsif city == "LONDON"
  puts "Visit The Tower of London."
elsif city == "ROME"
  puts "Visit Colosseo."
else
  puts "Oh, you don't like to visit any of those cities."
end

print "Which city do you like to visit? Paris, London or Rome? "
case gets.chomp.upcase
  when "PARIS"  then puts "Visit Le Musee de Louvre."
  when "LONDON" then puts "Visit The Tower of London."
  when "ROME"   then puts "Visit Colosseo."
  else puts "Oh, you don't like to visit any of those cities."
end

print "Which city do you like to visit? Paris, London or Rome? "
city = gets.chomp.upcase
puts "Visit Le Musee de Louvre."  if city == "PARIS"
puts "Visit The Tower of London." if city == "LONDON"
puts "Visit Colosseo."            if city == "ROME"
puts "Oh, you don't like to visit any of those cities." if
  not (city == "PARIS" or city == "LONDON" or city == "ROME")

for i in 5..10
  puts i
end

3.times { puts "I love NY" }

I love NY
I love NY
I love NY

配列とハッシュ

arr = [ "Cat", "Dog", "Rabbit" ]
arr.each do | animal |
  puts animal
end

arr = %w[ Cat Dog Rabbit ]

e_f = { "Cat" => "Chat", "Dog" => "Chien", "Rabbit" => "Lapin" }
e_f.each do | en, fr |
  puts "English: #{en} = French: #{fr}"
end

English: Cat = French: Chat
English: Dog = French: Chien
English: Rabbit = French: Lapin

ブロック

(5...11).each do |i|
  puts i
end

do [| param[, ... ] |]
  statement
  [ ... ]
end

bl = proc { |i| puts i }
(5...11).each { |n| bl.call(n) }

5
6
7
8
9
10

procs = {}
procs[:plus]     = proc { |n| puts n[0] + n[1] }
procs[:minus]    = proc { |n| puts n[0] - n[1] }
procs[:multiply] = proc { |n| puts n[0] * n[1] }
procs[:divide]   = proc { |n| puts n[0] / n[1] }
operation = { :divide => [9, 2], :plus => [6, 8], :multiply => [8, 1], :minus => [9, 7] }
operation.each { |k, n| procs[k].call(n) }   # call every appropriate operation dynamically

Loop

loop do
  puts gets
end

while (ans = gets.chomp.upcase) != "END"
  puts ans
end

count = 0
begin
  ans = gets.chomp.upcase
  break if ans == "QUIT"
  next  if ans == "SILENT"
  redo  if ans == "AGAIN"
  puts ans
end until ans == "END" or (count += 1) >= 5

def max (a, b)
  (a > b) ? a : b
end

puts max(2, 10)     ---> 10

PREDICATE ? TRUE : FALSE

def max (m, *a)
  a.each { |b| m = b if b > m }
  m
end

puts max(1.732, 1_024, Math::PI/180*60)    ---> 1024
puts max("Cat", "Dog", "Rabbit")        ---> Rabbit

def min (*a)
  m = a[0]
  a.each do |n|
    return nil unless (n.is_a? Numeric)
    m = n if n < m
  end
  m
end

puts min(1.732, 1_024, Math::PI/180*60)    ---> 1.0471975511966
puts min("Cat", "Dog", "Rabbit")        ---> nil

class Name [< Parent]
  [statement[ ... ]]

  [attr_reader :variable[, ... ]]
  [attr_writer :variable[, ... ]]

  [def initialize[(param[, ... ])]
    [statement[ ... ]]
   end]

  [def method[(param[, ... ])]
    [statement[ ... ]]
    end]
  [ ... ]
end

# for a CD containing multi tracks of music
class MusicCD
  TYPE_ALBUM  = 12 # 12cm CD
  TYPE_SINGLE =  8 # 8cm CD
  @@count = 0

  attr_reader :type, :code, :title, :production, :player, :resume, :tracks
  attr_writer :resume

  def initialize(type, code, title, production, player, tracks)
    @@count += 1
    @type = type
    @code = code
    @title = title
    @production = production
    @player = player
    @tracks = tracks
    @resume = 1
  end

  def MusicCD.getCount
    @@count
  end

  def playTrack(number)
    return nil if number <= 0 or number > tracks.length
    @resume = number
    @tracks[number-1]
  end

  def resume
    @tracks[@resume-1]
  end

  def to_s
    "title=#{@title}\n production=#{@production}\n player=#{@player}"
  end
end

# for each music track
class Music
  attr_reader :title, :time, :feature

  def initialize(title, time, feature)
    @title = title
    @time = time
    @feature = feature
  end

  def to_s
    "title=#{@title}\n playing time=#{@time}\n featuring=#{@feature}"
  end
end

# for songs
class Song < Music
  def initialize(title, time, feature, lyrics)
    super(title, time, feature)
    @lyrics = lyrics
  end

  def getSongCard
    @lyrics
  end

  def to_s
    super + "\n [#{@lyrics[0]}]"
  end
end

# catalog of CDs
class Catalog
  attr_reader :cds
  attr_writer :cds

  def initialize
    @cds = Array.new
  end

  def to_s
    "Catalog has #{@cds.length} CDs"
  end
end

音楽CD

cat = Catalog.new
tracks = []
tracks << Music.new(
  "Horn Concerto in D major, K386b(412/514)", "8:11", "Alan Civil")
tracks << Music.new(
  "Horn Concerto in E flat major, K495", "16:35", "Alan Civil")
cat.cds << MusicCD.new(
  MusicCD::TYPE_ALBUM,
  "464 717-2",
  "Mozart: The Horn Concertos",
  "PHILIPS",
  "Neville Marriner/Academy of St Martin in the Fields; horn: Alan Civil",
  tracks
  )

tracks = []
lyrics = [
  "There's a small hotel",
  "With a wishing well",
  "I wish that we were there together",
  "There's a bridal suite",
  "One room bright and neat",
  "Complete for us to share together"
  ]
tracks << Song.new(
  "THERE'S A SMALL HOTEL", "2:47", "Richard Rogers, Lorenz Hart", lyrics)
lyrics = [
  "My funny Valentine",
  "Sweet comic Valentine",
  "You make me smile with my heart"
  ]
tracks << Song.new(
  "MY FUNNY VALENTINE", "3:53", "Richard Rogers, Lorenz Hart", lyrics)
lyrics = [
  "Blue moon",
  "You saw me standing alone",
  "Without a dream in my heart",
  "Without a love of my own"
]
tracks << Song.new(
  "BLUE MOON", "3:10", "Richard Rogers, Lorenz Hart", lyrics)
cat.cds << MusicCD.new(
  MusicCD::TYPE_SINGLE,
  "POCJ-2130",
  "The Rogers And Hart Songbook Vol.2",
  "VERVE",
  "vocal: Ella Fitzgerald, conductor: Buddy Bregman",
  tracks
  )

puts MusicCD.getCount        ---> 2

puts cat

Catalog has 2 CDs

cat.cds.each { |cd| puts cd }

title=Mozart: The Horn Concertos
 production=PHILIPS
 player=Neville Marriner/Academy of St Martin in the Fields; horn: Alan Civil
title=The Rogers And Hart Songbook Vol.2
 production=VERVE
 player=vocal: Ella Fitzgerald, conductor: Buddy Bregman

正規表現

def findCD (cds, tag)
  cds.each do |cd|
    return cd if cd.title =~ /#{tag}/
  end
  nil
end

cd = findCD(cat.cds, "Songbook Vol.2")
if cd != nil
  puts cd.playTrack(2)
end

title=MY FUNNY VALENTINE
 playing time=3:53
 featuring=Richard Rogers, Lorenz Hart
 [My funny Valentine]

メソッドの追加

class Catalog
  def [](tag)
    cds.each do |cd|
      return cd if cd.title =~ /#{tag}/
    end
    nil
  end
end

cd = cat["Songbook Vol\.2"]
puts cd.playTrack(3) if cd

title=BLUE MOON
 playing time=3:10
 featuring=Richard Rogers, Lorenz Hart
 [Blue moon]

class Catalog
  def play(music)
    cds.each { |cd|
      cd.tracks.each { |track|
        return [cd, track] if track.title =~ /#{music}/i
      }
    }
    nil
  end
end

music = cat.play("horn .* e flat major")
puts music if music

title=Mozart: The Horn Concertos
 production=PHILIPS
 player=Neville Marriner/Academy of St Martin in the Fields; horn:Alan Civil
title=Horn Concerto in E flat major, K495
 playing time=16:35
 featuring=Alan Civil

ブロックの実行

class Catalog
  def search
    list = Array.new
    cds.each { |cd| list << cd if yield(cd) }
    list
  end
end

puts cat.search { |cd| cd.type == MusicCD::TYPE_SINGLE }

title=The Rogers And Hart Songbook Vol.2
 production=VERVE
 player=vocal: Ella Fitzgerald, conductor: Buddy Bregman

puts cat.search { |cd| cd.production =~ /philips/i }

title=Mozart: The Horn Concertos
 production=PHILIPS
 player=Neville Marriner/Academy of St Martin in the Fields; horn:Alan Civil

def lyric?(cd, tag)
  found = false
  cd.tracks.each { |track|
    if track.class == Song
      track.getSongCard.each { |line|
        if line =~ /#{tag}/i
          found = true
          break
        end
      }
    end
    break if found
  }
  found
end

puts cat.search { |cd| lyric?(cd, "dream") }

title=The Rogers And Hart Songbook Vol.2
 production=VERVE
 player=vocal: Ella Fitzgerald, conductor: Buddy Bregman

File.open( "request.txt", "r" ) do |file|
  file.each do |line|
    music = cat.play(line.chomp)
    if not music
      puts line.chomp + " was not found"
    else
      cd, track = music
      printf( "CD: %s %s; %s, %s\n", cd.production, cd.code, cd.title, cd.player )
      printf( "Music: \"%s\", time: %s\n", track.title, track.time )
    end
  end
end

<request.txt>
k386
small hotel
Valentine
stardust

CD: PHILIPS 464 717-2; Mozart: The Horn Concertos, Neville Marriner/Academy of St Martin in the Fields; horn:Alan Civil
Music: "Horn Concerto in D major, K386b(412/514)", time: 8:11
CD: VERVE POCJ-2130; The Rogers And Hart Songbook Vol.2, vocal: Ella Fitzgerald, conductor: Buddy Bregman
Music: "THERE'S A SMALL HOTEL", time: 2:47
CD: VERVE POCJ-2130; The Rogers And Hart Songbook Vol.2, vocal: Ella Fitzgerald, conductor: Buddy Bregman
Music: "MY FUNNY VALENTINE", time: 3:53
stardust was not found

歌詞カード

song = cat.play("Small Hotel")
if song
  cd, track = song
  card = track.getSongCard
  card.collect! do |line|
    line + "\n"
  end
  File.open("smallHotel.card", "w") do |file|
    file.write(card)
  end
end

<timec.rb>
module Timec
  def Timec.seconds(time)    # time format [hh:]mm:ss
    ss, mm, hh = time.split(":").reverse
    hh = "0" unless hh
    ((hh.to_i * 60) + mm.to_i) * 60 + ss.to_i
  end
end

require "timec"

cd, track = cat.play("My Funny Valentine")
puts Timec.seconds(track.time) if track

233

組込み

puts Time.now
puts Time.new.seconds("2:14:35")

Fri Jul 11 15:06:23 +0900 2008
undefined method `seconds' for Time:Class (NoMethodError)

<timex.rb>
module Timex
  def seconds(time)
    ss, mm, hh = time.split(":").reverse
    hh = "0" unless hh
    ((hh.to_i * 60) + mm.to_i) * 60 + ss.to_i
  end
end

require "timex"

class Time
  include Timex
end

puts Time.new.seconds("2:14:35")

8075

require "timex"

class Music
  include Timex
  include Comparable

  def timeSeconds
    seconds(@time)
  end

  def <=>(other)
    seconds(@time) - seconds(other.time)
  end
end

cd, track1 = cat.play("My Funny Valentine")
cd, track2 = cat.play("Blue Moon")
fmt = "%s is %d seconds long\n"
printf(fmt, "My Funny Valentine", track1.timeSeconds)
printf(fmt, "Blue Moon", track2.timeSeconds)

track = (track1 >= track2) ? track1 : track2
puts track.title + " is longer"

My Funny Valentine is 233 seconds long
Blue Moon is 190 seconds long
MY FUNNY VALENTINE is longer

cd = cat["Songbook"]
songs = cd.tracks.sort
songs.each { |song| puts "#{song.title}, #{song.time}" }

THERE'S A SMALL HOTEL, 2:47
BLUE MOON, 3:10
MY FUNNY VALENTINE, 3:53

ミューテックス

require "thread"
mutex = Mutex.new
command = ""    # shared by threads via mutex

# player: plays the music in a thread
player = Thread.new(cat.play("K495")) do |cd|
  track = cd[1]
  time = track.timeSeconds
  button = ""
  begin
    Thread.pass
    mutex.synchronize do
      button = command
    end
    case button
    when "play"
      puts "--- playing #{track.title} remaining #{time} seconds"
      sleep(3)
      time -= 3
    when "pause"
      puts "--- pausing"
      Thread.stop
    end
  end until time <= 0
  Thread.exit
end

# controller: in the main thread, this operates the player 
begin
  input = gets.chomp.downcase
  if input =~ /^(play|pause|stop)$/
    mutex.synchronize do
      command = input
    end
    case input
    when "play"
      player.wakeup if player.status == "sleep"
    when "stop"
      Thread.kill(player)
      break
    end
  end
end until player.status == nil
player.join

play
--- playing Horn Concerto in E flat major, K495 remaining 995 seconds
--- playing Horn Concerto in E flat major, K495 remaining 992 seconds
--- playing Horn Concerto in E flat major, K495 remaining 989 seconds
pause
--- pausing
play
--- playing Horn Concerto in E flat major, K495 remaining 986 seconds
--- playing Horn Concerto in E flat major, K495 remaining 983 seconds
pause
--- pausing
stop

begin
  statement[ ... 
    raise([error_type,]["error message"][,trace_back])
   ... ]
rescue [error_type]
  statement[ ... ]
[ ... ]
else
  statement[ ... ]
ensure
  statement[ ... ]
end

require "thread"
mutex = Mutex.new
command = ""    # shared by threads via mutex

### exception handling
begin

  # player: plays the music in a thread
  print "Music title: "
  music = gets.chomp
  player = Thread.new(cat.play(music)) do |cd|
    Thread.main.raise RuntimeError, "'#{music}' was not found" unless cd
    track = cd[1]
    time = track.timeSeconds
    button = ""
    begin
      Thread.pass
      mutex.synchronize do
        button = command
      end
      case button
      when "play"
        puts "--- playing #{track.title} remaining #{time} seconds"
        sleep(3)
        time -= 3
      when "pause"
        puts "--- pausing"
        Thread.stop
      end
    end until time <= 0
    Thread.exit
  end

  # controller: in the main thread, this operates the player 
  begin
    input = gets.chomp.downcase
    if input =~ /^(play|pause|stop)$/
      mutex.synchronize do
        command = input
      end
      case input
      when "play"
        player.wakeup if player.status == "sleep"
      when "stop"
        Thread.kill(playing)
        break
      end
    end
  end until player.status == nil

rescue RuntimeError
  puts $!
else
  player.join
end

Music title: stardust
'stardust' was not found

require "mysql"

mysql = Mysql.new("hostname", "username", "password", "database")
res = mysql.query("SELECT * FROM table_name")
res.each_hash do |row|
  row.each do |column, value|
    puts "#{column} = #{value}"
  end
end
mysql.close

<データベース>
CREATE DATABASE MusicCD CHARACTER SET utf8;
CREATE USER musicfan;
GRANT ALL PRIVILEGES ON MusicCD.* TO musicfan;

<テーブル>
CREATE TABLE tbl_cds (
  id         INTEGER NOT NULL AUTO_INCREMENT,
  cd_type    CHAR(6) NOT NULL,
  code       VARCHAR(30) NOT NULL,
  title      TEXT NOT NULL,
  production VARCHAR(30) NOT NULL,
  player     TEXT NOT NULL,
  PRIMARY KEY (id)
);
CREATE TABLE tbl_musics (
  id      INTEGER NOT NULL AUTO_INCREMENT,
  cd_id   INTEGER NOT NULL,
  title   TEXT NOT NULL,
  time    CHAR(8) NOT NULL,
  feature TEXT NOT NULL,
  FOREIGN KEY (cd_id) REFERENCES tbl_cds (id),
  PRIMARY KEY (id)
);
CREATE TABLE tbl_songs (
  music_id INTEGER NOT NULL,
  lyric    TEXT NOT NULL,
  line     SMALLINT NOT NULL,
  FOREIGN KEY (music_id) REFERENCES tbl_music (id)
);

class MusicCD
  attr_reader :cd_id   # DB access key

  def addMusic(music)
    @tracks << music if music.is_a? Music
  end

  def set_cd_id!(id)
    @cd_id = id
    self
  end
end

class Catalog
  def addCD(cd)
    @cds << cd if cd.is_a? MusicCD
  end

  def each
    @cds.each do |cd|
      yield(cd)
    end
  end
end

begin
  # access DB and process
rescue
  # to catch an error and to do its post process
end

catalog = Catalog.new
begin
  # access DB and process
  if not (mysql = Mysql.new("localhost", "musicfan", "", "MusicCD"))
    raise ":0: failed to connect MusicCD"
  end
  if not (res = mysql.query("SELECT * FROM tbl_cds"))
    raise ":1: failed to access tbl_cds"
  end
  res.each_hash do |r|
    type = (r["cd_type"] == "ALBUM") ? MusicCD::TYPE_ALBUM : MusicCD::TYPE_SINGLE
    catalog.addCD(MusicCD.new(type, r["code"], r["title"],
      r["production"], r["player"], []).set_cd_id!(r["id"]))
  end

  catalog.each do |cd|
    if not (res = mysql.query("SELECT * FROM tbl_musics WHERE cd_id = #{cd.cd_id}"))
      raise ":1: failed to access tbl_musics"
    end
    res.each_hash { |r|
      if not (song = mysql.query("SELECT lyric FROM tbl_songs WHERE music_id = #{r["id"]} ORDER BY line"))
        res.free
        raise ":1: failed to access tbl_songs"
      end
      if song.num_rows > 0   # this music is a song
        lyrics = Array.new
        while (lyric = song.fetch_row)
          lyrics << lyric
        end
        music = Song.new(r["title"], r["time"], r["feature"], lyrics)
      else
        music = Music.new(r["title"], r["time"], r["feature"])
      end
      song.free
      cd.addMusic(music)
    }
  end
  mysql.close

rescue
  # to catch an error and to do its post process
  puts "#{$!} #{mysql.error}"
  if $! =~ /:0:/
    exit
  else
    mysql.close
  end
end

puts catalog
puts catalog.play("Blue Moon")

Catalog has 2 CDs
title=The Rogers And Hart Songbook Vol.2
 production=VERVE
 player=vocal: Ella Fitzgerald, conductor: Buddy Bregman
title=BLUE MOON
 playing time=3:10
 featuring=Richard Rogers, Lorenz Hart
 [Blue moon]

address =~ /東京都/s

変数

変数の有効範囲

代入

field = %w[ Dog ]
house = field       # copy the reference to the object
field << "Fox"
puts house
puts "=========="
field = %w[ Dog ]
house = field.dup   # copy the object
field << "Fox"
puts house

Dog
Fox
==========
Dog

class Animo
  def initialize
    @cage = [] 
  end

  def put(animal)
    @cage << animal
  end

  def show
    puts @cage
  end
end

field = Animo.new
field.put("Dog")
house = field       # copy the reference to the object
field.put("Fox")
house.show
puts "=========="
field = Animo.new
field.put("Dog")
house = field.dup   # copy the object, yet @cage has the reference
field.put("Fox")
house.show

Dog
Fox
==========
Dog
Fox

メソッドの書き換え

パラメータの省略

end end end !

• Programming Ruby 第1版
  事実上のRubyの公式マニュアルで原書は英語です。2008年4月には第2版の日本語訳も出ています。 2008年秋にはRuby 1.9に対応した原書の第3版が出る予定のようです。
• Rubyの公式サイト
  日本の公式サイトです。
• Rubyリファレンスマニュアル
  Rubyは日本人のまつもとゆきひろ氏が開発した言語で、このサイトが真のリファレンスマニュアルです。