Ruby keyword arguments advantages and use cases

keyword_arguments.rb

####
# 1. Simple assertion of required arguments
####
#   - You can forget #fetch
#   - You get a better error, and always on the line where method is defined

def search(options = {})
  query = options.fetch(:query)
end
search() # => KeyError: key not found :query

def search(query:)
  # ...
end
search() # => ArgumentError: missing keyword: query


####
# 2. Easy providing of default values
####
#   - Using #fetch can be cumbersome

def search(page: 1, per_page: nil, all: true)
  # ...
end

def search(options = {})
  options[:page] ||= 1
  options[:all]  ||= true  # problem: gets executed when `all: false` is passed
end

def search(options = {})
  options[:page] = options.fetch(:page) { 1 }
  options[:all]  = options.fetch(:all)  { true }
end


####
# 3. Shortness
####

def search(options = {})
  quizzes = Quiz.dataset
  quizzes = quizzes.search(options[:q]) if options[:q]
  quizzes = quizzes.where(category: options[:category]) if options[:category]
  quizzes = quizzes.paginate(Integer(options[:page]), Integer(options[:per_page])) if options[:per_page]
  quizzes
end

def search(q: nil, category: nil, page: 1, per_page: nil)
  quizzes = Quiz.dataset
  quizzes = quizzes.search(q) if q
  quizzes = quizzes.where(category: category) if category
  quizzes = quizzes.paginate(Integer(page), Integer(per_page)) if per_page
  quizzes
end


####
# 4. You can easily extract "special" options
####

def make_request(params = {})
  raise_errors = params.fetch(:raise_errors) { true }
  params.delete(:raise_errors)

  response = api.request(params)
  raise HTTPError if response.status.between?(400, 500) && raise_errors
  response
end

def make_request(raise_errors: true, **params)
  response = api.request(params)
  raise HTTPError if response.status.between?(400, 500) && raise_errors
  response
end

####
# 5. Sometimes it can really help you write elegant code
####
#  - `tries` cannot be in the method body, because retry executes the whole method again, so `tries` gets reinitialized

def get_weather_report(tries: 3)
  WeatherApi.get_report
rescue Timeout::Error
  tries -= 1
  retry if tries > 0
  raise
end

####
# 6. It's completely interchangable with Hash as options
####
#  - Everything below works

def search(**options)
  options #=> Hash
  make_request("search", options)
  make_request("search", **options)
end

def search(options = {})
  options #=> Hash
  make_request("search", options)
  make_request("search", **options)
end

make_request(options = {})
make_request(**options)