module WhyIsNobody using Refinements end # lazyatom.com/refinements

Disclaimer This is not a sales pitch for refinements. I am not going to show you how they are amazing and will solve all your programming problems. They might be good… but also they might be bad. They might even be terrible! Using refinements might make your application implode, or make you smell really bad, or lower your credit rating, or make your cat regard you with an even stronger level of apathetic disdain. Please do not hold me responsible if use of refinements leaves you with an unexplainable rash, or an overwhelming sense of ennui. Other side effects may include: syntax itch, nil nausea, const-ipation, drowsiness, and global interpreter lockjaw.

What are refinements? A mechanism to change the behaviour of an object in a limited and controlled way

module Shouting refine String do def shout self.upcase + "!" end end end

module Shouting refine String do def shout self.upcase + "!" end end end class Thing using Shouting "Hello".shout # => "HELLO!" end

module Shouting refine String do def shout self.upcase + "!" end end end class Thing using Shouting "Hello".shout # => "HELLO!" end "Hello".shout # => NoMethodError: undefined method 'shout' for "Oh no":String

module TexasTime refine Time do def to_s if hour > 12 "Afternoon, y’all!" else super end end end end

module TexasTime refine Time do def to_s if hour > 12 "Afternoon, y’all!" else super end end end end class RubyConf using TexasTime Time.parse("12:00").to_s # => "2015-11-16 12:00:00" Time.parse("14:15").to_s # => "Afternoon, y’all!" end

module TexasTime refine Time do def to_s if hour > 12 "Afternoon, y’all!" else super end end end end class RubyConf using TexasTime Time.parse("12:00").to_s # => "2015-11-16 12:00:00" Time.parse("14:15").to_s # => "Afternoon, y’all!" end Time.parse("14:15").to_s # => "2015-11-16 14:15:00"

using ( a developer’s guide )

class Thing "hello".shout # => "HELLO!" end using Shouting

class Thing "hello".shout # => "HELLO!" end using Shouting

class Thing def greet "hello".shout end end Thing.new.greet # => "HELLO!" using Shouting

class Thing def greet "hello".shout end end Thing.new.greet # => "HELLO!" using Shouting

class Thing def greet "hello" end end Thing.new.greet using Shouting .shout # => NoMethodError

class Thing using Shouting end class Thing "hello".shout # => NoMethodError end

class Thing using Shouting class OtherThing "hello".shout # => "HELLO!" end end

class Thing using Shouting class OtherThing < Thing "hello".shout end end # => NoMethodError

class Thing using Shouting class OtherThing < Thing "hello".shout end end # => "HELLO!"

class Thing using Shouting class OtherThing "hello".shout # => "HELLO!" end end

class Thing using Shouting end class Thing::OtherThing "hello".shout # => NoMethodError end

class Thing using Shouting def run yield end end Thing.new.run do "hello".shout end # => NoMethodError

Lexical Scope

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level A

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level Parent none A Parent Top Level

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level Parent none A Parent Top Level

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level Parent none A Parent Top Level

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting

Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout

Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout # => “HELLO!”

Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting

file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting

Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout

Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting # => NoMethodError file: thing.rb class Thing using Shouting "hello".shout end "goodbye".shout

file: thing.rb using Shouting class Thing "hello".shout end "goodbye".shout Top Level Parent none Refinements Shouting A Parent Top Level Refinements Shouting

Top Level Parent none Refinements Shouting A Parent Top Level Refinements Shouting file: thing.rb using Shouting class Thing "hello".shout end "goodbye".shout

Top Level Parent none Refinements Shouting A Parent Top Level Refinements Shouting file: thing.rb using Shouting class Thing "hello".shout end "goodbye".shout # => “HELLO!” # => “GOODBYE!”

Refinements are activated in current and nested lexical scopes

file: thing.rb class Thing using Shouting end class Thing "hello".shout end

file: thing.rb class Thing using Shouting end class Thing "hello".shout end Top Level Parent none Refinements empty

file: thing.rb class Thing using Shouting end class Thing "hello".shout end Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting

file: thing.rb class Thing using Shouting end class Thing "hello".shout end Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting B Parent Top Level Refinements empty

file: thing.rb class Thing using Shouting end class Thing "hello".shout end Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting B Parent Top Level Refinements empty

same class ≠ same scope

file: thing.rb class Thing using Shouting end class Other < Thing "hello".shout end

file: thing.rb class Thing using Shouting end class Other < Thing "hello".shout end Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting B Parent Top Level Refinements empty

class hierarchy ≠ scope hierarchy

different file = different scope

file: thing.rb class Thing using Shouting def greet "hello".shout end end Thing.new.greet

file: thing.rb class Thing using Shouting def greet "hello".shout end end Thing.new.greet Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting

file: thing.rb class Thing using Shouting def greet "hello".shout end end Thing.new.greet Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting Thing#greet Lexical scope A

file: thing.rb class Thing using Shouting def greet "hello".shout end end Thing.new.greet Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting Thing#greet Lexical scope A

file: thing.rb class Thing using Shouting def greet "hello".shout end end Thing.new.greet Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting Thing#greet Lexical scope A

Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting Thing#greet Lexical scope A file: thing.rb class Thing using Shouting def greet "hello".shout end end Thing.new.greet

Top Level Parent none Refinements empty A Parent Top Level Refinements Shouting Thing#greet Lexical scope A file: thing.rb class Thing using Shouting def greet "hello".shout end end Thing.new.greet # => “HELLO!”

methods are evaluated using the lexical scope at their definition

file: thing.rb class Thing using Shouting def run yield end end Thing.new.run do "hello".shout end # => NoMethodError

file: thing.rb class Thing using Shouting def run yield end end Thing.new.run do "hello".shout end Top Level Refinements empty A Parent Top Level Refinements Shouting Thing#greet Lexical scope A

file: thing.rb class Thing using Shouting def run yield end end Thing.new.run do "hello".shout end Top Level Refinements empty A Parent Top Level Refinements Shouting Thing#greet Lexical scope A Main#block Lexical scope Top level

blocks are evaluated using the lexical scope at their definition

Refinements use lexical scope

You get a new lexical scope when 1. Entering a different file 2. opening a class or module definition 3. running code from a string using “eval”

Refinement principles 1. activated within current and nested scopes 2. scope hierarchy is not the same as class hierarchy 3. different files get different top level scopes 4.methods are evaluated using lexical scope at their definition 5. blocks are evaluated using lexical scope at their definition

Let’s use refinements!

1. Monkey patching

class String def camelize self.split("_").map(&:capitalize).join end end "ruby_conf_2015".camelize # => "RubyConf2015"

/app/.bundle/gems/ruby/2.1.0/gems/activesupport-4.2.1/lib/active_support/ inflector/methods.rb:261:in `const_get': wrong constant name Admin/adminHelper (NameError) from /app/.bundle/gems/ruby/2.1.0/gems/activesupport-4.2.1/lib/active_support/ inflector/methods.rb:261:in `block in constantize' from /app/.bundle/gems/ruby/2.1.0/gems/activesupport-4.2.1/lib/active_support/ inflector/methods.rb:259:in `each' from /app/.bundle/gems/ruby/2.1.0/gems/activesupport-4.2.1/lib/active_support/ inflector/methods.rb:259:in `inject' from /app/.bundle/gems/ruby/2.1.0/gems/activesupport-4.2.1/lib/active_support/ inflector/methods.rb:259:in `constantize' from /app/.bundle/gems/ruby/2.1.0/gems/activesupport-4.2.1/lib/active_support/ core_ext/string/inflections.rb:66:in `constantize' from /app/.bundle/gems/ruby/2.1.0/gems/actionpack-4.2.1/lib/ abstract_controller/helpers.rb:156:in `block in modules_for_helpers' from /app/.bundle/gems/ruby/2.1.0/gems/actionpack-4.2.1/lib/ abstract_controller/helpers.rb:144:in `map!' from /app/.bundle/gems/ruby/2.1.0/gems/actionpack-4.2.1/lib/ abstract_controller/helpers.rb:144:in `modules_for_helpers' from /app/.bundle/gems/ruby/2.1.0/gems/actionpack-4.2.1/lib/action_controller/ metal/helpers.rb:93:in `modules_for_helpers'

Monkey-patching Refinements breaks API expectations cannot affect distant code makes code harder to debug leaves lexical clue when active

2. Managing API changes

# Ruby 1.9 "hello".chars # => # # Ruby 2.0+ "hello".chars # => ["h", "e", "l", "l", "o"]

module OldChars refine String do def chars; each_char; end end end "hello".chars # => ["h", "e", "l", "l", “o"] using OldChars "hello".chars # => #

3. DSLs

describe "Ruby" do it "should bring happiness" do developer = Developer.new(uses: "ruby") developer.should be_happy end end

describe "Ruby" do it "should bring happiness" do developer = Developer.new(uses: "ruby") developer.should be_happy end end

module RSpec refine Object do def should(expectation) expectation.satisfied_by?(self) end end end using RSpec 123.should eq 123 # => true false.should eq true # => false

4. Internal access control

module UserAdmin refine User do def purge! user.associated_records.delete_all! user.delete! end end end # in app/controllers/admin_controller.rb class AdminController < ApplicationController using UserAdmin def purge_user User.find(params[:id]).purge! end end

So… why is nobody using refinements?

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No content

“Because they’re just bad.”

YOU ARE EVERYTHING THAT IS WRONG WITH EVERYTHING

“ermm — are they? Why do you think that?”

“Because they’re just bad.”

awesome (adj.) — inspiring awe. Credit: pfala/Flickr

$ gem install awesome # this is not awesome

http://blog.honeybadger.io/benchmarking-ruby- refinements/ “TL;DR: Refinements aren’t slow. Or at least they don’t seem to be slower than ‘normal’ methods”

1. Lack of understanding?

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2. Adding using everywhere is a giant pain in the ass?

3. Rails (and Ruby) doesn't use them

$ fgrep 'refine ' -R rails | wc -l # => 0

$ fgrep 'refine ' -R ruby-2.2.3/ext | wc -l # => 0

4. Implementation quirks?

using Shouting "hello".shout # => “HELLO" "hello".respond_to?(:shout) # => false "hello".send(:shout) # => NoMethodError ["how", "are", "you"].map(&:shout) # => NoMethodError

5. Refinements solve a problem that nobody has?

6. The rise of Object-Oriented Design?

class Shouter def initialize(string) @string = string end def shout @string.upcase + "!" end end shouted_hello = Shouter.new("hello") shouted_hello.shout # => "HELLO!"

I don’t know. 1. Lack of understanding 2. Adding using everywhere is a pain in the ass 3. Rails (and Ruby) doesn’t use them 4. Implementation quirks 5. They solve a problem that nobody has 6. Object-oriented design

I don’t know. 1. Lack of understanding 2. Adding using everywhere is a pain in the ass 3. Rails (and Ruby) doesn’t use them 4. Implementation quirks 5. They solve a problem that nobody has 6. Object-oriented design 7. Because other people have told us that they are “bad”.

Psssst! This isn’t a talk about refinements.

Sharing opinions is good

Blindly adopting opinions is… less good

Dude, globes suck.

Awesome! Sucks.

“I think you’ll find it’s a bit more complicated than that.”

Explore for yourselves

Thanks! James Adam @lazyatom lazyatom.com/refinements