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CHRIS GAFFNEY @gaffneyc Collective Idea Harmony harmonyapp.com 

Keyword Arguments Module#prepend Enumerable#lazy Refinements Bonus Round 

Keyword Arguments Module#prepend Enumerable#lazy Refinements Bonus Round 

BASIC USAGE # Common patterns def foo(options = {}) headers = options.delete(:headers) end def foo(options = {}) options[:headers] ||= {} end # With keyword arguments def foo(headers: {}) end foo # headers = {} foo(headers: { "Content-Type: text/html" }) # headers = { "Content-Type: text/html" } foo(test: "not an argument") # ArgumentError: unknown keyword: test foo("headers" => "Will a string work?") # ArgumentError: unknown keyword: headers 

VAROPTS def foo(headers: {}, **options) end foo(test: "not an argument") # headers = {} # options = { test: "not an argument" } 

ALL THE OPTIONS # required argument, varargs, keyword arguments, varopts def foo(required, *args, kw: nil, **options) end foo(5) foo(5, 6, 7, 8) foo(5, 6, 7, 8, kw: true) foo(5, 6, 7, 8, kw: true, test: "too true") # required = 5 # args = [ 6, 7, 8 ] # kw = true # options = { :test => "too true"} 

SUPER class Foo def awesome_method(keyword: "go") puts keyword end end class Bar < Foo def awesome_method(keyword: "bar") super end end Bar.new.awesome_method # => go # Keyword arguments are not automatically passed to super 

Keyword Arguments Module#prepend Enumerable#lazy Refinements Bonus Round 

MODULE#PREPEND class Foo < Object end Foo.ancestors # => [ Foo, Object, BasicObject ] 

MODULE#PREPEND class Foo < Object include Bar end Foo.ancestors # => [ Foo, Bar, Object, BasicObject ] 

MODULE#PREPEND class Foo < Object include Bar include Baz end Foo.ancestors # => [ Foo, Bar, Baz, Object, BasicObject ] 

MODULE#PREPEND class Foo < Object include Bar include Baz prepend Buz end Foo.ancestors # => [ Buz, Foo, Bar, Baz, Object, BasicObject ] 

MODULE#PREPEND class Foo < Object include Bar include Baz prepend Buz prepend Bat end Foo.ancestors # => [ Bat, Buz, Foo, Bar, Baz, Object, BasicObject ] 

ALIAS METHOD CHAIN class Foo def bar puts "bar" end end # Standard pattern: reopen the class and alias_method_chain class Foo def bar_with_baz puts "baz" bar_without_baz end alias_method :bar_without_baz, :bar alias_method :bar, :bar_with_baz end Foo.new.bar # baz # bar 

USE PREPEND INSTEAD module Baz def bar puts "baz" super end end class Foo prepend Baz def bar puts "bar" end end # Or class_eval since prepend is private Foo.class_eval { prepend Baz } Foo.new.bar # baz # bar 

Keyword Arguments Module#prepend Enumerable#lazy Refinements Bonus Round 

BASIC USAGE %w(1 2 3 4).map(&:to_i).select(&:even?) # [ 2, 4 ] # Intermediary steps: # [ "1", "2", "3", "4" ] => [ 1, 2, 3, 4 ] => [ 2, 4 ] %w(1 2 3 4).inject([]) do |memo, val| val = val.to_i memo << val if val.even? memo end # [ 2, 4 ] %w(1 2 3 4).lazy.map(&:to_i).select(&:even?) # :map>:select> %w(1 2 3 4).lazy.map(&:to_i).select(&:even?).to_a # [ 2, 4 ] %w(1 2 3 4).lazy.map(&:to_i).select(&:even?).each { |v| puts v } # 2 # 4 

INFINITE / LARGE SETS (0..1_000_000_000).select(&:even?).take(10) # I don't know... it crashed my computer (0..1_000_000_000).lazy.select(&:even?).take(10).to_a # [0, 2, 4, 6, 8, 10, 12, 14, 16, 18] 

Keyword Arguments Module#prepend Enumerable#lazy Refinements Bonus Round 

BASIC USAGE 

BASIC USAGE module Foo refine String do def hello "world" end end end 

BASIC USAGE module Foo refine String do def hello "world" end end end # Pretend this is in bar.rb require "foo" # Refinements currently have file scope using Foo class Bar def foo "".hello end end puts Bar.new.foo # => "world" 

Keyword Arguments Module#prepend Enumerable#lazy Refinements Bonus Round 

#to_h # Hashes return themselves { foo: "bar" }.to_h # { :foo => "bar" } # Structs have a representation FooBar = Struct.new(:foo, :bar) FooBar.new("baz", "buz").to_h # => { :foo => "baz", :bar => "buz" } # Nil gives an empty hash nil.to_h # => {} # OpenStruct! OpenStruct.new(:foo => "bar").to_h # => { :foo => "bar" } # Be more permissive on what types of objects we can accept def foo(hash) if hash.respond_to?(:to_h) hash = hash.to_h else raise ArgumentError, "zomg I want a hash" end end 

# We alread have %w for strings strings = %w(test foo bar) # [ "test", "foo", "bar" ] %i / %I 

# We alread have %w for strings strings = %w(test foo bar) # [ "test", "foo", "bar" ] # Now we have %i for symbols symbols = %i(test foo bar) # [ :test, :foo, :bar ] %i / %I 

# We alread have %w for strings strings = %w(test foo bar) # [ "test", "foo", "bar" ] # Now we have %i for symbols symbols = %i(test foo bar) # [ :test, :foo, :bar ] # Or use %I if you need interpolation symbols = %I(test #{"foo"}) # [ :test, :foo ] %i / %I 

# In previous versions of ruby this line can be expensive: fork do 1 + 1 end # Ruby deployment is typically done with multiple processes. When each process # takes a big chunk of memory it's common to see: # Copy on Write makes fork calls cheaper because memory is only copied when it # is changed. # If one process takes 200Mb then 10 processes means 2Gb # Copy-on-Write can reduce that footprint significantly for subprocesses. Copy-on-Write (COW) 

ENCODING # unicode.rb puts "¿Cómo estás?" # 1.9 $ ruby unicode.rb unicode.rb:1: invalid multibyte char (US-ASCII) unicode.rb:1: invalid multibyte char (US-ASCII) # 2.0 $ ruby unicode.rb ¿Cómo estás? File.read("unicode.rb").encoding # # unset LANG LC_CTYPE LC_ALL File.open("send_test.rb", "r:utf-8") { |f| f.read }.encoding # 

CHRIS GAFFNEY @gaffneyc Collective Idea Harmony harmonyapp.com