Question

I have never seen this construct for building a hash. do_stuff(records: records) Does this only work in a parameter list being sent to a method? Is it documented anywhere? I know it is Ruby 1.9+.

records = { 
  'example.com' => '1.2.3.4',
  'hello.com' => '44.33.22.22',
}

def do_stuff(data = {} )
 puts data
end

do_stuff(records: records)

Answer 1

There are two things going on here. The { key: value } syntax is new in Ruby 1.9. It is equivalent to { :key => value }.

Also, Ruby methods have some syntactical sugar that allows you to pass in a hash literal as the last argument of the method without including the curly braces. This is not new in Ruby 1.9. So

do_stuff(key: value)

Is equivalent to

do_stuff({ key: value })

Just to remind you, this only works if the hash is the last argument to the method.