Vidul Nikolaev Petrov

arr = (1..10).to_a
 
 str = arr * ', '
 str = arr.join(', ')

MyFile.create "test.txt"
MyFile.add "test.txt", "some content"
MyFile.remove "test.txt"

module FileEasy
 
  def self.included(subject)
    subject.extend(ClassMethods)
  end
 
  module ClassMethods
   alias_method :delete, :remove
   alias_method :unlink, :remove
 
    def create(filename)
      File.open(filename, "w")
    end
    def add(filename, text)
      File.open(filename, "a"){ |f| f < < text }
    end
    def remove(filename)
      File.delete(filename)
    end
  end
 
end

require 'fileeasy'
 
class MyClass
  include FileEasy
end
 
MyFile.create "text.txt"
MyFile.add "text.txt", "test content"
MyFile.remove "text.txt"

class Class
  def attr(arg)
    arg = arg.to_s
    if self.class_variables.include?(arg)
      class_eval %(def self.#{arg.sub(/^\@\@/, '')}; #{arg}; end)
    else
      raise ArgumentError, "No such class attribute", caller
    end
  end
end
 
class Test
  @@class_var = "class variable value"
 
  attr :@@class_var
end
 
puts Test.class_var => "class variable value"

AoH = [{"z"=>26}, {"g"=>7}, {"r"=>18}, {"a"=>1}, {"v"=>22}]
 
# sort by key
AoH.map{|e| e.to_a.flatten}.sort{|x,y| x[0] < => y[0]}
# sort by value
AoH.map{|e| e.to_a.flatten}.sort{|x,y| x[1] < => y[1]}

# RoR source code:
# File vendor/rails/actionpack/lib/action_view/helpers/text_helper.rb, line 34
def truncate(text, length = 30, truncate_string = "...")
  if text.nil? then return end
  l = length - truncate_string.chars.length
  text.chars.length > length ? text.chars[0...l] + truncate_string : text
end
 
# My point of view:
def truncate(text, _length = 30, truncate_string = "...")
  text[0..(_length-1)] + truncate_string
end

class Object
  def arguments?(*methods)
    methods.each do |method|
      begin
        rval = self.method(method).arity
        if rval > 0
          puts "'#{method}' takes fixed (#{rval}) number of argument"
        elsif rval < 0
          puts "'#{method}' takes variable number of arguments"
        elsif rval == 0
          puts "'#{method}' takes no arguments"
        end
      rescue
       puts $!
      end
    end
  end
end
 
String.new.arguments?(:size, :to_i, :scan, :flatten)

class MyString < String
  # not really useful
  alias + concat
 
  # emulates Array '*' method
  def *(string)
    self.split('').inject('') do |s1,c|
      s1 + c + string
    end
  end
 
  # emulates Array '-' method
  def /(string)
    (self.split('') - string.split('')).to_s
  end
 
  # chars' delimiter
  def delimiter(string)
    self.*(string).sub /.$/, ''
  end
 
end
 
a = MyString.new("abcdef")
b = MyString.new("ABCDEF")
 
puts a * ':'
puts a / (b + "a")
puts a.delimiter(":")
 
#a:b:c:d:e:f:
#bcdef
#a:b:c:d:e:f

class Array
  def to_h
    arr = self.dup
    if arr.size % 2 == 0
        Hash[*arr]
    else
        Hash[*arr < < nil]
    end
  end
end