notes - Secrets of Standard Library

source/talks/unleash-the-secrets-of-the-standard-library-with-simpledelegator,-forwardable,-and-more/notes/aeon-notes.md

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+author: Anton Stroganov (@aeon)
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+# Secrets of the Standard Library - Jim Gay - [@saturnflyer](http://twitter.com/saturnflyer)
+
+- Recommended: Ruby under a microscope - amazing book to learn how ruby internals actually work
+
+- Anyway, check out /lib directory in ruby source, there's actually a lot of stuff, written in ruby, that people don't know about or use.
+- Delegator
+	- require 'delegate'
+	- wraps a class and passes any method calls it does not have to the wrapped class with method_missing.
+	- Keep the User class clean, create a UserDecorator class to wrap it and have methods that don't relate directly to user's base functionality (like user.birth_year... calls User.born.year).
+	- define == to compare the object to the wrapped object and self... hmm.
+	- but better to just use SimpleDelegator because it handles this stuff for you as well as preventing other problems.
+	- __get_obj__ and __set_obj__ are standard, but kind of ugly
+	- User < SimpleDelegator - would be nice to call the wrapped object as user, not __get_obj__ 
+		- Could :alias it, but that gets repetitive too
+		- self.inherited used to define behaviour to run when a class is instantiated by a child class...
+		- can use it to figure out the child class name, and use klass.send() to create the aliases automatically.
+	- Delegator removes methods from Kernel module so that the missing methods get passed on to the wrapped object... neat.
+	- drapergem/draper is interesting too
+	- So this is very useful when you try to redefine methods or use method_missing
+		- def DelegateClass - 
+			- klass = Class.new(Delegator) - create a new class with same methods etc. as an existing class
+		- you could do something like
+			- UserDecorator < DelegateClass(User)
+			- but that loses the "User" in ancestry because it makes an anonymous copy of the class, so it can be more confusing...
+	- the rabbit hole goes deeper... basically can do lots of your own magic with this
+- Forwardable
+	- User has an address
+	- You could say, User.address.city, but that requires the rest of the system to know that user has an address which has a city... really want to just be able to say User.city
+	- you can write a module, Forward
+		- and use class_eval to define a method that will be defined in the context of the current class
+		- example use:
+
+			class Person
+				extend Forward
+				forward :address, :city
+			end
+
+		- which will pass call to Person.city to address.city.
+	- but standard library already has a tool to do it:
+
+		require 'forwardable'
+		class Person
+			extend Forwardable
+			delegate [:city, :number, :postal_code] => :address
+		end
+
+	- ActiveSupport adds a couple of extra features:
+		- allow_nil
+		- prefix to define a prefix for the methods to be delegated
+	- could use this to make third party code hot-swappable... delegate "save_exception" method to a class that could be changed later...
+	- SingleForwardable is for class level methods, Forwardable is for defining instance level methods 
+- SimpleDelegator - run time behaviour
+- Forwardable - load time behaviour
+
+- similar projects
+	- saturnflyer/casting
+	- myobie/rep
+	- stevenharman/dumb_delegator
+	- elight/modest_presenter
+
+- clean-ruby.com