Question

I’m trying to write a function that would apply the function to just one item if it’s not a collection, or else apply that function to each of the collections elements. For example:

replace spaces with underscores

foo 'a bear' => 'a_bear'
foo ['a bear', 'a bee'] => ['a_bear', 'a_bee']

Is this possible?

Answer 1

It depends on how you define “collection”. The most natural option would probably be either “any Enumerable” or even “anything with an each method”. However this leads to a problem because Strings are Enumerable, too – in ruby 1.8, at least.

If you only need it to work with arrays, it’s easy:

def foo(x)
  if x.is_a? Array
    x.map {|item| foo(item)}
  else
    # Do something with x
  end
end