santosh79

#The clone method also copies over the singleton methods of the receiver
porsche = Object.new
def porsche.number_of_wheels
  4
end

puts "porsche has #{porsche.number_of_wheels}"
porsche_clone = porsche.clone

puts "porsche's clone has #{porsche_clone.number_of_wheels}"

santosh79

#Struct.new returns a class object that has attributes that you pass in
Car = Struct.new(:wheels, :rpm) #Car is a Class object that has attributes *wheels* & *rpm* now

porsche = Car.new(4,1600)

#Since Struct.new is basically an expression returning a Class object - even the following would work

class Car < Struct.new(:wheels,:rpm)
end

santosh79

#Keeping track of number instances of a class without actually creating getter and setter methods

class Foo
  @count = 0
  #Create a singleton class for self - which is currently the Foo class object
  class << self
    attr_accessor :count
  end

  def initialize

santosh79

#A typical ActiveRecord Model would need to extends ActiveRecord::Base, like so:

class Person < ActiveRecord::Base
end

#And now we have access to class & instance level methods like find & save
p = Person.find 1
p.save

#A non-inheritance based re-write of the above code - i.e. one that does not require

santosh79

#When a proc calls a return - it returns from the context

def method
  puts "at top of method"
  p = Proc.new { return }
  p.call
  puts "at bottom of method"
end

puts "before call"

santosh79

#Re-writing a method inside itself can be done in ruby

def meth1
  def meth1
  end
  puts "in old method"
end

meth1 #This prints "in old method"
meth1 #This does not

santosh79

#We can force the execution order of methods

class Foo
  def start
    def stop
    end
  end
end

f = Foo.new

santosh79

module Accessor
  def my_attr_accessor(*names)
    names.each do |name|
      ivar_name = "@#{name}"

      define_method(name) do
        instance_variable_get(ivar_name)
      end

      define_method("#{name}=") do |val|

santosh79

module Accessor
  def my_attr_accessor(*names)
    names.each do |name|
      class_eval %{
        def #{name}
          @#{name}
        end

        def #{name}=(val)
          @#{name} = val

santosh79

module Hello
  def say_hello
    puts "hello"
  end
end

[String, Array, Hash].each do |cls|
  cls.class_eval { include Hello }
end