Examples of new features in Ruby 2.3.0

ruby-2.3.0.rb

# These are examples of new features in Ruby 2.3.0

#---------------------------------------------------------------------------
## Did You Mean?
"Typos suck less now".revers

# NoMethodError: undefined method `revers' for "Typos suck less now":String
# Did you mean?  reverse
#                reverse!


#---------------------------------------------------------------------------
## The safe navigation operator
## AKA The lonely operator

# This could return a User object or nil
user = User.first

# In Ruby 2.2.x you'd do this to make sure you don't raise an exception if user is nil:
if user && user.is_awesome?
  # ...
end

# In Ruby 2.3.0 you can use the safe navigation operator instead:
if user&.is_awesome?
  # ...
end

# It will return nil if the user object is nil

# This is super handy when you need to chain these calls together:
event_name = api_data&.events&.first&.text&.strip

# Think about how succinct this would be when doing any scraping!

#---------------------------------------------------------------------------
## Hash.dig + Array.dig

film = { 
  id: 1234, 
  title: "Back to the Future", 
  casts: {
    cast: [ 
      { name: "Michael J. Fox", character: "Marty McFly" }, 
      { name: "Crispin Glover", character: "George McFly" } 
    ], 
    crew: [ 
      { name: "Robert Zemeckis", role: "Director" } 
    ] 
  } 
}

# To get the first cast member's name, just dig it up
film.dig(:casts, :cast, 0, :name) # => "Michael J. Fox"

# C'mon. WHAAAAT?


#---------------------------------------------------------------------------
## Numeric.positive? and Numeric.negative?

# Useful for filtering Enumerables
[1, 12, -2, 100, -99, 44].select(&positive?) # => [1, 12, 100, 44]
[1, 12, -2, 100, -99, 44].select(&negative?) # => [-2, 99]


#---------------------------------------------------------------------------
## Enumerable.grep_v

# Allows you to find items that don't match you expression in one go
star_wars = %w(Vader Yoda Luke Han Leia Chewbacca Jabba)

everyone_but_luke = star_wars.grep(/a/)
only_luke = star_wars.grep_v(/a/)


#---------------------------------------------------------------------------
## String.freeze

# Freezing a string makes it immutable (unchangeable)
# This could very well be the default come Ruby 3.0

# The Old Way™
CONSTANT = "Not really a "
CONSTANT << " constant" # Not really a constant, totally OK with Ruby!

FROZEN = "Can't touch this".freeze
FROZEN << " Hammer!" # RuntimeError: can't modify frozen String

# The big change here is how it's allocated in memory
# Freeze now only allocates one object in memory

# 1000 objects for the same string 1000 times!
1000.times.map{ "Heavy duty".object_id }.uniq.size #=> 1000

# Just 1 object! Handy if you refer to strings a lot.
1000.times.map{ "Lightweight".freeze.object_id }.uniq.size #=> 1


#---------------------------------------------------------------------------
# Hash.to_proc

car = {
  make: "Porsche",
  model: "911",
  doors: 2,
  colour: "gunmetal",
  cylinders: 12,
  horsepower: 400,
  price: 120000,
  origin: "Germany" 
}

features = %i[make model origin]
features.map(&car) # => ["Porsche", "911", "Germany"]

extended_features = %i[make interior torque]
extended_features.map(&car) # => ["Porsche", nil, nil]


#---------------------------------------------------------------------------
# Hash.fetch_values

# This is a stricter version of Hash.values_at
# If the key we're searching for it throws an error

car.values_at(:horsepower, :torque) # => [400, nil]
car.fetch_values(:horsepower, :torque) #=> KeyError: key not found: :torque


#---------------------------------------------------------------------------
# Hash Comparisons (Superset and Subset)

one = { title: "Hateful Eight" }
some = { title: "Hateful Eight", director: "Quentin Tarantino" }
all = { title: "Hateful Eight", director: "Quentin Tarantino", year: 2015 }
random = { rockets: true }

one < some # => true (one is a strict subset of some)
some > some # => false 
some >= some # => true