Some advanced ruby features

RubyAdvancedFeatures

#the new tap method of ruby will always return itself, but lets you play with!
data = (1..10).to_a
data.tap{|x| print x}.to_a.join(', ')
p


#alias will redirect method calls to method with a different name, useful for api changing
class SomeClass  
  def new_method(x)
    p "The value is #{x}"
  end
  
  alias :old_method :new_method
end

SomeClass.new.old_method(20)


# Array.grep - the beauty of unix grep right into Ruby Array
puts((1..100).grep(38..44))   #=> [38, 39, 40, 41, 42, 43, 44]
c = IO.constants
puts c.grep(/SEEK/)         #=> ["SEEK_END", "SEEK_SET", "SEEK_CUR"]
puts c.grep(/SEEK/) {|v| IO.const_get(v) } #=> [2, 0, 1]

#delegate - get rid of all the method declarations that just delegate others using Ruby's delegate support
require 'delegate'
class Actual
  def a_method
    puts "Method inside Actual"
  end
end

class MyDelegator < DelegateClass(Actual)
  def initialize
    @actual = Actual.new
    super(@actual)
  end
end
MyDelegator.new.a_method

#freeze - make your variables pseudo readonly
my_hash = {:a => 1, :b =>2}.freeze

# my_hash[:a] = 20 #=> throws exception

#included vs. extended - included makes module methods your instance methods, extend will make the same methods as class methods
module AModuleToInclude
  def self.included(mod)
    puts "#{self} included in #{mod}"
  end  
  
  def self.extended(mod)
    puts "#{self} extended in #{mod}"
  end
  
  def a_method
    puts "From a_method"
  end
end

class AClass
  include AModuleToInclude
  extend AModuleToInclude
end
#this line makes use of the include
AClass.new.a_method
#this line makes use of the extend
AClass.a_method

#Use of * for argument list
def many_args(*args)
  puts "Inside many_args = " ,*args  
end
many_args( [1, 2, 3, 4])


#class_eval - write a code in string without making it look like a string using this
class ClassWithEval
  class_eval <<-EVAL
    def string_method(arg)
      puts arg
    end
  EVAL
end

ClassWithEval.new.string_method('hi')

#instance_eval - write code as if your are right inside a class for your instance
class ClassWithInstanceEval
 def initialize
   @secret = 99
 end
end
k = ClassWithInstanceEval.new
k.instance_eval { puts @secret }   #=> 99

#inherited - fires this hook when a new subclassing takes place
class Foo
  def self.inherited(subclass)
     puts "New subclass: #{subclass}"
  end
end

class Bar < Foo
end

class Baz < Bar
end