Ruby 2: some new things

Ruby 2some new things

David A. BlackLead DeveloperCyrus Innovation@david_a_black

Ruby Blind meetupApril 10, 2013

About me• Rubyist since 2000 (Pickaxe baby)

• Lead Developer, Cyrus Innovation

• Developer, author, trainer, speaker, event organizer

• Author of The Well-Grounded Rubyist

• Co-founder of Ruby Central

• Chief author of scanf.rb (standard library)

Today's topics• Lazy enumerators

• Module#prepend

• String#bytes and friends

• Keyword arguments

• Miscellaneous changes and new features

Lazy enumeratorsWhat's wrong with this code?

# find the first 10 multiples of 3

(0..Float::INFINITY).select {|x| x % 3 == 0 }.first(10)

Lazy enumerators

It runs forever!

# find the first 10 multiples of 3

(0..Float::INFINITY).select {|x| x % 3 == 0 }.first(10)

Lazy enumerators

# find the first 10 multiples of 3

(0..Float::INFINITY).lazy.select {|x| x % 3 == 0 }.first(10)

Lazy enumerators

# find the first 10 multiples of 3

(0..Float::INFINITY).lazy.select {|x| x % 3 == 0 }.first(10)

=> [0, 3, 6, 9, 12, 15, 18, 21, 24, 27]

Lazy enumerators

r = 0..Float::INFINITYs = 0..Float::INFINITY

r.zip(s).first(5) # runs forever

Lazy enumerators

r = 0..Float::INFINITYs = 0..Float::INFINITY

r.lazy.zip(s).first(5)

=> [[0, 0], [1, 1], [2, 2], [3, 3], [4, 4]]

Lazy enumerators

# From Ruby source documentation

fib = Enumerator.new do |y| a = b = 1 loop do y << a a, b = b, a + b endend

fib.zip(0..Float::INFINITY).first(5) # runs forever

Lazy enumerators

fib = Enumerator.new do |y| a = b = 1 loop do y << a a, b = b, a + b endend.lazy

fib.zip(0..Float::INFINITY).first(5)

# => [[1, 0], [1, 1], [2, 2], [3, 3], [5, 4]]

Lazy enumerators• can be created via #lazy on an Enumerable

• [1,2,3].lazy

• (0..Float::INFINITY).lazy

• an_enumerator.lazy (see Fibonacci example)

Module#prependWhat will the output be?

class Person def talk puts "Hello" endend

module Yeller def talk super puts "I said... HELLLLLOOO!!!!" endend

class Person include Yellerend

david = Person.newdavid.talk

Module#prepend

class Person def talk puts "Hello" endend

module Yeller def talk super puts "I said... HELLLLLOOO!!!!" endend

class Person include Yellerend

david = Person.newdavid.talk

# => Hello

p Person.ancestors

# => [Person, Yeller, Object, Kernel, BasicObject]

Module#prependWhat will the output be?

class Person def talk puts "Hello" endend

module Yeller def talk super puts "I said... HELLLLLOOO!!!!" endend

class Person prepend Yellerend

david = Person.newdavid.talk

Module#prepend

class Person def talk puts "Hello" endend

module Yeller def talk super puts "I said... HELLLLLOOO!!!!" endend

class Person prepend Yellerend

david = Person.newdavid.talk

# => Hello I said... HELLLLLOOO!!!!

p Person.ancestors

# => [Yeller, Person, Object, Kernel, BasicObject]

Module#prepend• Puts the module *before* the receiver (class or module) in the method lookup path• A good way to avoid messing with alias

class Person def talk puts "Hello!" endend

class Person alias old_talk talk def talk old_talk puts "I said... HELLLLLOOO!!!!" endend

String#bytes/each_byte(and friends)

• String#bytes, #lines, #chars, #codepoints now return arrays

• #each_byte/line/char/codepoint still return enumerators

• Saves you having to do #to_a when you want an array

Keyword arguments

def my_method(a, b, c: 3) p a, b, cend

my_method(1, 2) # 1 2 3my_method(1, 2, c: 4) # 1 2 4

Lets you specify a default value for a parameter, and use the parameter's name in your method call

Keyword arguments

def my_method(a, b, *array, c: 3) p a, b, array, cend

my_method(1, 2, 3, 4, c: 5) # 1, 2, [3, 4], 5

Non-keyword arguments still work essentially the same way that they did.

Keyword arguments

def my_method(a, b, *array, c: 3, **others) p a, b, array, c, othersend

my_method(1, 2, 3, 4, c: 5, d: 6, e: 7) # 1, 2, [3, 4], 5, {:d=>6, :e=>7}

Extra keyword arguments get passed along in the **others parameter.

Keyword arguments

def my_method(a, b, c) p a, b, cend

my_method(1, 2, z: 3) # 1 2 {:z=>3}

Hash-like arguments that don't correspond to a named argument get passed along as a hash.

Keyword arguments

class Person attr_accessor :name, :email, :age

def initialize(name: "", email: "", age: 0) self.name = name self.email = email self.age = age endend

david = Person.new(email: "[email protected]", name: "David", age: Float::INFINITY)

Order doesn't matter:

Miscellaneous• %i{} and %I{}

• Default encoding now UTF-8 (no need for magic comment)

• Struct#to_h, nil#to_h, Hash#to_h

• Kernel#Hash (like Array, Integer, Float)

• const_get now parses nested constants

• Object.const_get("A::B::C")

• #inspect doesn't call #to_s any more

• Questions?

• Comments?

David A. BlackLead DeveloperCyrus Innovation@david_a_black

Ruby Blind meetupApril 10, 2013