How do I loop over a hash of hashes?

You'll want to recurse through the hash, here's a recursive method:

def ihash(h)
  h.each_pair do |k,v|
    if v.is_a?(Hash)
      puts "key: #{k} recursing..."
      ihash(v)
    else
      # MODIFY HERE! Look for what you want to find in the hash here
      puts "key: #{k} value: #{v}"
    end
  end
end

You can Then take any hash and pass it in:

h = {
    "x" => "a",
    "y" => {
        "y1" => {
            "y2" => "final"
        },
        "yy1" => "hello"
    }
}
ihash(h)

I little improved Travis's answer, how about this gist:

https://gist.github.com/kjakub/be17d9439359d14e6f86

class Hash

  def nested_each_pair
    self.each_pair do |k,v|
      if v.is_a?(Hash)
        v.nested_each_pair {|k,v| yield k,v}
      else
        yield(k,v)
      end
    end
  end

end

{"root"=>{:a=>"tom", :b=>{:c => 1, :x => 2}}}.nested_each_pair{|k,v|
  puts k
  puts v
}

Value is a Hash to so you need iterate on it or you can get only values:-

h.each do |key, value|
  puts key
  value.each do |k,v|
    puts k
    puts v
  end
end

or

h.each do |key, value|
  puts key
  value.values.each do |v|
    puts v
  end
end