Terser way of generating deeply nested hash

I need to generate a Ruby hash that looks like this:

{ "children" => [
  { "children" => [
    { "children" => [
      { "children" => [] }
    ]}
  ]}
]}

... for an arbitrary level of nesting. So far the best I've come up with is:

def nested_hash(levels)
  return {} if levels  [] }
  children = root['children']
  (levels - 1).times { children = (children  [] }).first['children'] }
  root
end

This doesn't seem particularly terse or elegant. Can anyone offer suggestions on making this more terse or elegant?

Recursion perhaps?

def nested_hash(levels)
  return if levels  [ nested_hash(levels - 1) ].compact }
end

Or it could be

def nested_hash(levels)
  return nil if levels  array.nil? ? [] : [array] }
end

if you prefer handling the nil upfront, instead of removing it with compact

In either case, nested_hash(3) will get you

{"children"=>[
  {"children"=>[
    {"children"=>[]}
  ]}
]}

Note that unlike yours, these ones will return nil when levels is zero or less. So you'll want to do the {} fallback elsewhere, e.g. hsh = nested_hash(x) || {}.

StackExchange Code Review Q#16090, answer score: 4