Rails is Magical

But how?

TIME

> rails console
> 2.days.ago
=> Sat, 28 Feb 2015 22:31:59 UTC +00:00
1.month.from_now
=> Thu, 02 Apr 2015 22:32:24 UTC +00:00 

Routes

Rails.application.routes.draw do
  resources :cats
  root 'cats#index' 

Is Rails a dsl?

• Matz thinks so
• (DSL: Domain Specific Language)

Duck Typing

Static Typing

public int add(int a, int b){
    return a + b
}

public String add(String a, String b){
    return a + b
}

Dynamic Typing

def add(a, b)
    a + b
end

Duck typing

If it walks like a duck...

duck typing is a style of typing in which an object's methods and properties determine the valid semantics, rather than its inheritance from a particular class or implementation of an explicit interface

-Wikipedia

Duck Type Checking

#Ruby
> 2.respond_to?(:+)
 => true

#Python
def is_leaf(node):
    try:
        if tree.label:
            return True
    except AttributeError:
        return False

Duck Punching Time

What is Duck Punching?

• A way to modify a class at run time
  • Even if you didn't create it
• "Reopen" a class and change it
• AKA monkey patching

Danger!

• Can lead to obtuse code
• But in the hands of a pro, cool things can happen
  • Rails Active Support