Default values, required arguments, keyword arguments and splats in Ruby

Ruby 2 Keyword Arguments

https://robots.thoughtbot.com/ruby-2-keyword-arguments

def foo(bar: 'default')
  puts bar
end

foo # => 'default'
foo(bar: 'baz') # => 'baz'

options = {bar: 'bazinga'}
foo(options) # => 'bazinga'

Required keyword arguments

def foo(bar:)
  puts bar
end

foo # => ArgumentError: missing keyword: bar
foo(bar: 'baz') # => 'baz'

http://www.justinweiss.com/articles/fun-with-keyword-arguments/

def hello_message(greeting, time_of_day, first_name:, last_name:)
  "#{greeting} #{time_of_day}, #{first_name} #{last_name}!"
end

args = ["Morning"]
keyword_args = {last_name: "Weiss"}

hello_message("Good", *args, first_name: "Justin", **keyword_args) # => "Good Morning, Justin Weiss!"

Splat array into a list

def print(x,y) 
  "coordinates: (#{x},#{y})" 
end

print(34,45) => coordinates: (34,45)

coords = [12,56]
print(*coords) => coordinates: (12,56)

Splat keyword argument into a argument list

def print(x:, y:) 
  "coordinates: (#{x},#{y})" 
end

print(x:34, y:45) => coordinates: (34,45)

coords = {x:12, y:56}
print(**coords) => coordinates: (12,56)

Mix of regular arguments, keyword arguments, and splats:

def hello_message(greeting, time_of_day, first_name:, last_name:)
  "#{greeting} #{time_of_day}, #{first_name} #{last_name}!"
end

args = ["Morning"]
keyword_args = {last_name: "Weiss"}

hello_message("Good", *args, first_name: "Justin", **keyword_args) # => "Good Morning, Justin Weiss!"

Capture arguments with * and keyword arguments with **

def dual_argument_capturing_method(*args, **keyword_args)
  {args: args, keyword_args: keyword_args}
end

dual_argument_capturing_method(1, 2, 3, key: "value") # => {:args=>[1, 2, 3], :keyword_args=>{:key=>"value"}}