AHABHGK

1# :string 表示 symbol，:string.object_id == :string.object_id
2def tell_the_truth(options={})
3  if options[:profession] == :lawyer
4    'it could be believed that this is almost certainly not false.'
5  else
6    true
7  end
8end
9
10tell_the_truth
11# => true
12tell_the_truth :profession => :lawyer
13# => "it could be believed that this is almost certainly not false."
14a = {:profession => :lawyer, :string => 'hahha'} # 散列表
15tell_the_truth a
16# => "it could be believed that this is almost certainly not false."

1animals = ['lions', 'tigers', 'bears', 'duck']
2animals.each {|a| puts a}
3# lions
4# tigers
5# bears
6# duck
7#  => ["lions", "tigers", "bears", "duck"]

1class Fixnum
2  def my_times
3    i = self
4    while i > 0
5      i = i - 1
6      yield
7    end
8  end
9end
10
113.my_times {puts 'mangy moose'}
12# mangy moose
13# mangy moose
14# mangy moose
15#  => nil

1def call_block(&block)
2  block.call
3end
4
5def pass_block(&block)
6  call_block(&block)
7end
8
9pass_block {puts 'helloo'}
10# helloo
11#  => nil

14.class.superclass.superclass.superclass.superclass
2# Integer Numeric Object BasicObject nil
3
44.class.class.superclass.superclass.superclass.superclass
5# Integer Class Module Object BasicObject nil

1class Tree
2  attr_accessor :children, :node_name
3
4  def initialize(name, children = [])
5    @children = children
6    @node_name = name
7  end
8
9  def visit_all(&block)
10    visit &block
11    children.each {|c| c.visit_all &block}
12  end
13
14  def visit(&block)
15    block.call self
16  end
17end
18
19ruby_tree = Tree.new("Ruby", [Tree.new("Reia"), Tree.new("MacRuby")])
20ruby_tree.visit {|node| puts node.node_name}
21# Ruby
22ruby_tree.visit_all {|node| puts node.node_name}
23# Ruby
24# Reia
25# MacRuby

1module ToFile
2  def to_f
3    puts "mixin tofile"
4  end
5end
6
7class Person
8  include ToFile
9  attr_accessor :name
10
11  def initialize(name)
12    @name = name
13  end
14
15  def to_s
16    name
17  end
18end
19
20Person.new('matz').to_f
21# mixin tofile

1a = [5, 2, 4, 3, 1]
2b = a.sort # [1, 2, 3, 4, 5]
3a.any? {|i| i > 4} # true
4a.all? {|i| i > 4} # false
5c = a.collect {|i| i * 2} # [10, 4, 6, 8, 2]
6d = a.select {|i| i % 2 == 0} # [2, 4]
7a.member?(2) # true
8a.inject(10) do |acc, cur|
9  puts "acc: #{acc}, cur: #{cur}"
10  acc + cur
11end
12#  => 25

1'same' <=> 'same' # 0

1# rails
2class Department < ActiveRecord::Base
3  has_many :employees
4  has_one :manager
5end

1class NilClass
2  def blank?
3    true
4  end
5end
6
7class String
8  def blank?
9    self.size == 0
10  end
11end
12
13["", "person", nil].each do |e|
14  puts e unless e.blank?
15end
16# "person"

1class Roman
2  def self.method_missing name, *args
3    roman = name.to_s
4    roman.gsub("IV", "IIII")
5    roman.gsub("IX", "VIIII")
6    roman.gsub("XL", "XXXX")
7    roman.gsub("XC", "LXXXX")
8
9    (roman.count("I") +
10     roman.count("V") * 5 +
11     roman.count("X") * 10 +
12     roman.count("L") * 50 +
13     roman.count("C") * 100)
14  end
15end
16
17puts Roman.XII # 12