Ruby

a = '\n这是一个单引号的字符串，反斜线和变量插值不会被转义'

b = %q{这是一个不可转义的字符串}

c = "\n这是一个双引号的字符串，反斜线和变量插值会被转义\n#{a}"

d = %Q{\n這是一個常量字串，特殊内容同样会被转义\n}

e = <<BLOCK
这是一个以Heredoc方式书写的常量字符串，可转义，结尾标志不可缩进
BLOCK

f = <<-BLOCK
      这是一个可以缩进的Heredoc字符串
    BLOCK

g = <<~BLOCK
      这是一个可以缩进的Heredoc字符串
      缩进会被自动去掉，在2.3版本中引入
    BLOCK

h = %/\t这是一个可转义的的字符串\n/

class MyClass
  def the_method
    "general method"
  end
end

mc = MyClass.new
def mc.the_method
  "special for this instance."
end

mc.the_method

class Project < ActiveRecord::Base
  belongs_to :portfolio
  has_one    :project_manager
  has_many   :milestones
end

a = [1,'hi', 3.14, 1, 2, [4, 5]]

p a[2]           # 3.14
p a.[]（2）# 3.14
p a.reverse      # [[4, 5], 2, 1, 3.14, 'hi', 1]
p a.flatten.uniq # [1, 'hi', 3.14, 2, 4, 5]

hash = { :water => 'wet', :fire => 'hot' }
puts hash[:fire] # Prints:  hot

hash.each_pair do |key, value| # Or:  hash.each do |key, value|
puts "#{key} is #{value}"
end

# Prints:  water is wet
#          fire is hot

hash.delete :water # Deletes :water => 'wet'
hash.delete_if {|k,value| value=='hot'} # Deletes :fire => 'hot'

{ puts "Hello, World!" } # Note the { braces }
#or
do puts "Hello, World!" end

# 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!"

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 { puts closure_value }
end

setter, getter = create_set_and_get  # ie. returns two values
setter.call(21)
getter.call # => 21

def use_hello
  yield "hello"
end

# Invoke the above method, passing it a block.
use_hello {|string| puts string} # => 'hello'

array = [1, 'hi', 3.14]
array.each { |item| puts item }
# => 1
# => 'hi'
# => 3.14

array.each_index { |index| puts "#{index}: #{array[index]}" }
# => 0: 1
# => 1: 'hi'
# => 2: 3.14

(3..6).each { |num| puts num }
# => 3
# => 4
# => 5
# => 6

[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
# => Wrote some text.

(1..10).collect {|x| x*x} # => [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

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