Summary of Ruby 2.3's feature.

ruby_2_3_features.rb

# frozen_string_literal: true

class User
  attr_accessor :admin

  def initialize(options = {})
    @admin = options[:admin] || false
  end

  def admin?; @admin end
end

##
# 1. Safe navigation operator
##

user = User.new(admin: true)

if user && user.admin?
  puts 'User is admin!'
end

if user&.admin?
  puts 'User is admin! (2)'
end

user = nil

if user && user.admin?
  puts 'User is admin!'
end

if user&.admin?
  puts 'User is admin! (2)'
end

##
# 2. Frozen string literal
##

begin
  str = 'foo'
  str << 'bar'
rescue
  puts 'Strings are frozen by default o/'
end


##
# 3. Array#dig and Hash#dig
##

numbers = [[1, 2], [3, 4], [5, 6]]

puts numbers.dig(2, 1) #=> 6
puts numbers.dig(0, 2) #=> nil

dict = { x: 'foo', y: { z: 'bar' } }

puts dict.dig(:x) #=> "foo"
puts dict.dig(:y, :z) #=> "bar"
puts dict.dig(:y, :w) #=> nil

##
# 4. Hash comparison
##

a = { x: 1, y: 2 }
b = { x: 1 }

puts a >= b #=> true
puts a <= b #=> false
puts b <= a #=> true

##
# 5. Hash#to_proc
##

h = { x: 1, y: 2 }
p = h.to_proc

puts p.call(:y)

puts %i(x).map { |key| h[key] }
puts %i(x).map(&h)

##
# 6. Hash#fetch_values
##

begin
  h = { x: 1, y: 2 }
  puts h.values_at(:x, :y, :z)
  puts h.fetch_values(:x, :y, :z)
rescue KeyError
  puts 'Key not found'
end

##
# 7. Enumerable#grep_v
##

puts User.new.methods.grep(/admin/).first
puts User.new.methods.grep_v(/admin/).first

##
# 8. Numeric#positive? and #negative?
##

puts 1.positive?
puts -1.negative?

##
# 9. Did you mean?
##

'foobar'.to_foo