• 文档: http://www.ruby-doc.org/
  • mac 上用 dash 很方便, 免费, 可以与 emacs 集成
  • 命令行 可用 ri keyword 查看
  • Programming Ruby: The Pragmatic Programmer's Guide
• String 替换
  • String.tr('from', 'to') 是 字符 替换, 与 bash 的 tr 相同
  • String.sub('from', 'to') 是 字符串 替换, 可用 regexp
• .. Range, 不支持倒序, 有一堆方法见文档
  • ('a'..'e').to_a #⇒ [“a”, “b”, “c”, “d”, “e”]
  • ('a'…'e').to_a #⇒ [“a”, “b”, “c”, “d”]
• if … elsif … end, 不是 else if, 不是 elif, 写错也不会报错
• 猜数字:

  n = 100
  r = rand(10) + 1
  g = 0
   
  puts "I have a number between 1 .. #{n}"
   
  until g == r
    g = gets().to_i
    if g > r
      puts 'too big'
    elsif g < r
      puts 'too small'
    end
  end
   
  puts 'bingo'

• 4.times { puts 'IOU' } 代码块
  • 代码块 只占一行时, 用 { .. }
  • 代码块 占多行时, 用 do .. end
  • 代码块 可带有一个或多个参数 (1..10).each { |i| puts i }
• class Tree

  class Tree
    attr_accessor :children, :node_name
   
    def initialize(name, children = [])
      @children = children
      @node_name = name
    end
   
    def visit_all(&block)
      visit &block
      children.each { |c| c.visit_all &block }
    end
   
    def visit(&block)
      block.call self
    end
   
    def to_s
      s = "visiting entire tree\n"
      self.visit_all { |node| s += "#{node.node_name}\n" }
      s
    end    
   
  end
   
  ruby_tree = Tree.new( 'Ruby', 
                        [Tree.new('Reia'),
                         Tree.new('MacRuby')] )
   
  puts 'Visiting a node'
   
  ruby_tree.visit { |node| puts node.node_name }
  puts
   
  puts 'visiting entire tree'
  ruby_tree.visit_all { |node| puts node.node_name }

• 开放类: 类可随时 “打开” 修改先前的类定义

  class Numeric
    def inches
      self
    end
   
    def feet
      self * 12.inches
    end
   
    def yards
      self * 3.feet
    end
   
    def miles
      self * 5280.feet
    end
   
    def back
      self * -1
    end
   
    def forward
      self
    end
  end
   
  puts 10.miles.back
  puts 2.feet.forward

• module: 对 class 实现 mixin(混入) 功能, 类似 Java 的接口, 但 module 对 class 是不感兴趣的, 通过 duck type 对类调用:

  module ToFile
    def filename
      "object_#{self.object_id}.txt"
    end
   
    def to_f
      File.open(filename, 'w') { |f| f.write(to_s) }
    end
  end
   
  class Person
    include ToFile
    attr_accessor :name
   
    def initialize(name)
      @name = name
    end
   
    def to_s
      name
    end
  end
   
  Person.new('Xiaopei').to_f

  • 常用的 module
    • enumerable(枚举), include 后必须实现 each 方法
    • comparable(比较), include 后必须实现 ⇔ 方法
• method_missing

  class Roman
    def self.method_missing name, *args
      puts '==='
      puts name
      roman = name.to_s
      roman.gsub!('IV', 'IIII')
      roman.gsub!('IX', 'VIII')
      roman.gsub!('XL', 'XXXX')
      roman.gsub!('XC', 'LXXX')
   
      puts roman
      (roman.count('I') + 
       roman.count('V') * 5 +
       roman.count('X') * 10 +
       roman.count('L') * 50 + 
       roman.count('C') * 100)
    end
  end
   
  puts Roman.X
  puts Roman.XC
  puts Roman.XII
  puts Roman.X

  • 缺点: 增加调试难度
• 使用 module: 1)避免继承; 2)根据类名动态对类增加方法.

  module ActsAsCsv
    def self.included(base) 
      # Ruby will invoke the included method whenever
      # this module gets included into another
   
      # Object.extend:
      # Adds to obj the instance methods from each module 
      # given as a parameter.
      base.extend ClassMethods
    end
   
    module ClassMethods
      def acts_as_csv
        include InstanceMethods
      end 
    end
   
    module InstanceMethods
      def read
        @csv_contents = []
        filename = self.class.to_s.downcase + '.txt' 
        file = File.new(filename)
        @headers = file.gets.chomp.split(', ')
        file.each do |row|
          @csv_contents << row.chomp.split(', ')
        end 
      end
   
      attr_accessor :headers, :csv_contents
   
      def initialize
        read
      end 
   
      def each(&block)
        self.csv_contents.each do |row|
          yield CsvRow.new(@headers, row)
        end
      end
    end
  end
   
  class CsvRow
    def initialize(headers, values)
      @hash = Hash.new
      headers.each_index do |i|
        @hash[headers[i]] = values[i]
      end
    end
   
    def to_s
      @hash.to_s
    end
   
    def method_missing name, *args
      # name 默认是 symbol, 需 to_s
      @hash[name.to_s]
    end
  end
   
  class RubyCsv # no inheritance! You can mix it in include ActsAsCsv
    include ActsAsCsv
    acts_as_csv
  end
   
  m = RubyCsv.new
  puts m.headers.inspect
  puts m.csv_contents.inspect
   
   
  # 可配套 rubycsv.txt 使用
  # ruby, php
  # puts, echo
  # def, define
   
   
  # 其实上面的 module 和 class 的定义在目前功能下, 和下面的相等
  module ActsAsCsv
    def read
      @csv_contents = []
      filename = self.class.to_s.downcase + '.txt' 
      file = File.new(filename)
      @headers = file.gets.chomp.split(', ')
      file.each do |row|
        @csv_contents << row.chomp.split(', ')
      end 
    end
   
    attr_accessor :headers, :csv_contents
   
    def initialize
      read
    end 
  end
   
  class RubyCsv # no inheritance! You can mix it in include ActsAsCsv
    include ActsAsCsv
  end

bbatsov/ruby-style-guide · GitHub

• 空格

  sum = 1 + 2
  a, b = 1, 2
  1 > 2 ? true : false; puts 'Hi'
  [1, 2, 3].each { |e| puts e }
   
  e = M * c**2
   
  # No spaces after (, [ or before ], ).
  some(arg).other
  [1, 2, 3].length

• 空行

  def some_method
    data = initialize(options)
   
    data.manipulate!
   
    data.result
  end
   
  def some_method
    result
  end

• 过长

  # Limit lines to 80 characters.
  def send_mail(source)
    Mailer.deliver(to: 'bob@example.com',
                   from: 'us@example.com',
                   subject: 'Important message',
                   body: source.text)
  end
   
  # good
  num = 1_000_000

• def (with parentheses when there are arguments. Omit the parentheses when the method doesn't accept any arguments)

   def some_method
     # body omitted
   end
   
   def some_method_with_arguments(arg1, arg2)
     # body omitted
   end

• if

  # good
  if some_condition
    # body omitted
  end
   
  # Don't use parentheses around the condition of an if/unless/while, unless the **condition contains an assignment**
  if (x = self.next_value)
    # body omitted
  end
  # but it's still bad. Don't use the return value of = (an assignment) in conditional expressions.
  x = self.next_value
  if x
    # body omitted
  end

• ternary operator(?:), Use one expression per branch in a ternary operator, inline only

  result = some_condition ? something : something_else
   
  if some_condition
    nested_condition ? nested_something : nested_something_else
  else
    something_else
  end

• inline if (?: without :)

  # good
  do_something if some_condition
   
  # another good option
  some_condition and do_something

• Favor unless over if for negative conditions (or control flow or). And always positive case first(Never use unless with else).

  # good
  do_something unless some_condition
   
  # another good option
  some_condition or do_something

• case .. when .. else .. end

  case
  when song.name == 'Misty'
    puts 'Not again!'
  when song.duration > 120
    puts 'Too long!'
  when Time.now.hour > 21
    puts "It's too late"
  else
    song.play
  end
   
  kind = case year
         when 1850..1889 then 'Blues'
         when 1890..1909 then 'Ragtime'
         when 1910..1929 then 'New Orleans Jazz'
         when 1930..1939 then 'Swing'
         when 1940..1950 then 'Bebop'
         else 'Jazz'
         end

• each (不要用 for ¹⁾)

  arr = [1, 2, 3]
   
  # good
  arr.each { |elem| puts elem }

• loop .. break

  loop do
    puts val
    val += 1
    break unless val < 0
  end

• inline while/until

  do_something while some_condition
   
  do_something until some_condition

• Omit parentheses around parameters for methods that are part of an internal DSL (e.g. Rake, Rails, RSpec), methods that have “keyword” status in Ruby (e.g. attr_reader, puts) and attribute access methods. Use parentheses around the arguments of all other method invocations.

  class Person
    attr_reader :name, :age
   
    # omitted
  end
   
  temperance = Person.new('Temperance', 30)
  temperance.name
   
  puts temperance.age
   
  x = Math.sin(y)
  array.delete(e)

• Avoid return where not required for flow of control.

  # good
  def some_method(some_arr)
    some_arr.size # no return
  end

• If the first argument to a method begins with an open parenthesis, always use parentheses in the method invocation. For example, write f((3 + 2) + 1).
• Avoid self where not required. (It is only required when calling a self write accessor.)

  # good
  def ready?
    if last_reviewed_at > last_updated_at # self omitted
      worker.update(content, options)
      self.status = :in_progress
    end
    status == :verified
  end

• As a corollary, avoid shadowing methods with local variables unless they are both equivalent.

  class Foo
    attr_accessor :options
   
    # ok
    def initialize(options)
      self.options = options
      # both options and self.options are equivalent here
    end
   
    # bad
    def do_something(options = {})
      unless options[:when] == :later
        output(self.options[:message])
      end
    end
   
    # good
    def do_something(params = {})
      unless params[:when] == :later
        output(options[:message])
      end
    end
  end

• Use ||= freely to initialize variables, but don't use ||= to initialize boolean variables. (Consider what would happen if the current value happened to be false.)

  # set name to Bozhidar, only if it's nil or false
  name ||= 'Bozhidar'
   
  # bad - would set enabled to true even if it was false
  enabled ||= true
   
  # good
  enabled = true if enabled.nil?

• lambda

  # good
  lambda = ->(a, b) { a + b }
  lambda.(1, 2)

• { … }for single-line blocks.

  names = ['Bozhidar', 'Steve', 'Sarah']
   
  # good
  names.each { |name| puts name }
   
   
  # good
  names.select { |name| name.start_with?('S') }.map { |name| name.upcase }

• do…end for multi-line blocks.
• Use _ for unused block parameters.

  # good
  result = hash.map { |_, v| v + 1 }

• Signal exceptions using the fail method. Use raise only when catching an exception and re-raising it (because here you're not failing, but explicitly and purposefully raising an exception).

  begin
    fail 'Oops';
  rescue => error
    raise if error.message != 'Oops'
  end

详见文档, 这里记几条容易忘的规则:

• Always supply a proper to_s method for classes that represent domain objects.
• Consider using Struct.new, which defines the trivial accessors, constructor and comparison operators for you.
• Consider adding factory methods to provide additional sensible ways to create instances of a particular class.
• Prefer duck-typing over inheritance.
• Assign proper visibility levels to methods (private, protected) in accordance with their intended usage. Don't go off leaving everything public (which is the default).

• 完全 OO
• 判断和循环都能单行写

  > puts 'This appears to be true.' if x == 4
  This appears to be true.
   => nil
   
  > x = x + 1 while x < 10
   => nil
  > x
   => 10

• 文档: Class: Regexp (Ruby-Doc)
• 在线测试 & Quick Ref: Rubular: a Ruby regular expression editor and tester

• 替换标签

'[BOLD]Strategy[\BOLD]'.gsub(/\[BOLD\](.*?)\[\\BOLD\]/, '<em>\\1</em>'  #=> <em>Strategy</em>

• rvm: ruby version manager
• gem: a package manager

rails

Ruby 自 1.9 起加入了 json, 之前需要额外安装(apt-get install ruby-json). Ruby 更推荐的格式是 yaml. 而 php 需装扩展才能支持 yaml.

# encode
data = { name: 'dave', address: [ 'tx', 'usa' ], age: 17 } serialized = data.to_json
serialized # => {"name":"dave","address":["tx","usa"],"age":17}
File.open("data", "w") {|f| f.puts serialized}
 
# decode
serialized = File.read("data")
data = JSON.parse(serialized)
data # => {"name"=>"dave", "address"=>["tx", "usa"], "age"=>17}
 
# j 和 jj 分别是普通和美化输出 json 的方法 

• puppet

可使用 ` 或 %x( 区别?):

`date`                  # => "Mon Apr 13 13:25:58 CDT 2009\n"
`ls`.split[34]          # => "ext_c_win32ole.tip"
%x{echo "Hello there"}  # => "Hello there\n"