hopsoft

# define original class
class Example

  def say_hello
    puts "hello"
  end

end

# re-open the class

hopsoft

# define original class
class Example

  def say_hello
    puts "hello"
  end

end

# re-open the class and monkeypatch some of its existing functionality

hopsoft

# create a namespace to avoid naming collisions
module Example

  class String
    def length
      100
    end
  end

end

hopsoft

# add a kernel method to make it available to all objects
# this example also serves to illustrate that everything in Ruby is an object
module Kernel

  def say_hello
    puts "hello from #{self.class.name}"
  end

end

hopsoft

# add methods that provide the ability
# to dynamically call unknown methods on objects
def invoke(object, method_name)
  object.send(method_name)
end

def invoke_with_args(object, method_name, *args)
  object.send(method_name, *args)
end

hopsoft

module MagicShow

  def show
    method_name = params[:id]
    if respond_to? method_name
      send(method_name)
    else
      render :text => "That operation is not supported!", :layout => false
    end
  end

hopsoft

# setup a contrived class to demonstrate pattern dispatch
class Person
  attr_accessor :first_name
  attr_accessor :last_name
  attr_accessor :pets_name
  attr_accessor :mothers_maiden_name

  def drag_queen_name
    "#{pets_name} #{mothers_maiden_name}"
  end

hopsoft

# setup some data that will drive what methods get defined
$method_names = [:hello, :goodbye]

# define our example class
class Example
  # define some dynamic methods
  $method_names.each do |method_name|
    define_method(method_name) do |name|
      puts "#{method_name} #{name}!"
    end

hopsoft

# define our example class
class Example
  # catch all calls to methods that don't exist
  def method_missing(method_name, *args)
    puts "You called '#{method_name}' with these arguments: #{args.inspect}"
  end
end

# invoke methods that haven't been defined
Example.new.some_method # => You called 'some_method' with these arguments: []

hopsoft

class Proxy
  def initialize(object)
    @object = object
  end

  # forward all calls to the wrapped object
  def method_missing(method_name, *args)
    @object.send(method_name, *args)
  rescue 
    puts "#{method_name} is not supported by the wrapped object!"