Master the Object-Oriented Mindset in Ruby and Rails Week 1

According to Alan Kay, definition of object-oriented programming is made up of three pieces

• Messaging
• Local retention and protection and hiding of state-process
• Extreme late-binding of all things.

Late-Binding

Pendatic Example

find the ruby meeting room

1. Early binding Go left then right then 3rd door down

2. Middle binding Go to room 201
   • No matter where you start from, you will wind up in the room you want
3. Late binding Go to the front desk and someone will give you the directions
   • You can change the room location half an hour before the meeting starts

Real world examples

• On www, choose which server handles a request by passing all requests through a load-balancing proxy server.
• Inside a web app, hard coding in a global config file is early bound, late bound is storing this variable in a database table or key-value store.

Late-binding in Ruby

• a bareword is an undecorated data reference
  1. a variable
  2. a no arg method
  3. or a method parameter

my_class = MyClass.new
my_class.greeting

It provides flexibility and late-binding benefits in ruby, if we decide to change their implementation later, we can implement them as another form of bareword and save ourselves from rewriting our implementation.

Methods vs. Messages

In Ruby, messaging is implemented using object methods.

1. Messages are late-bound In some statically typed programming languages such as C++, object methods are early-bound by default unless prefixed with the virtual keyword.

2. Messages are discretionary
   • Null Object Pattern
3. Messages are one-way, no return values
   • In Ruby messages are two-way
4. Messages use commoditized formats