What does a splat operator do when it has no variable name?

Question

I was browsing through the Camping codebase when I saw a constructor with a splat being used like this:

class Fruit 
  def initialize(*)
  end
end

I tried looking up "splat with no variable name" on this site and Google, but I couldn't find anything besides info about splat being used with a variable name like this *some_var, but not without it. I tried playing around with this on a repl, and I tried stuff like:

class Fruit 
  def initialize(*)
      puts *
  end
end

Fruit.new('boo')

but that runs into this error:

(eval):363: (eval):363: compile error (SyntaxError)
(eval):360: syntax error, unexpected kEND
(eval):363: syntax error, unexpected $end, expecting kEND

If this question hasn't been asked already, can someone explain what this syntax does?

Answer 1

It behaves similar to *args but you cant refer to then in method body

def print_test(a, *)
  puts "#{a}"
end

print_test(1, 2, 3, 'test')

This will print 1.

Answer 2

Typically a splat like this is used to specify arguments that are not used by the method but that are used by the corresponding method in a superclass. Here's an example:

class Child < Parent
  def do_something(*)
    # Do something
    super
  end
end

This says, call this method in the super class, passing it all the parameters that were given to the original method.

source: Programming ruby 1.9 (Dave Thomas)