holiday_dec = {

:winter => {
   :christmas => ["Lights", "Wreath"],
   :new_years => ["Party Hats"]
 },
 :summer => {
   :fourth_of_july => ["Fireworks", "BBQ"]
 },
 :fall => {
   :thanksgiving => ["Turkey"]
 },
 :spring => {
   :memorial_day => ["BBQ"]
 }

}

def all_supplies_in_holidays(holiday_hash)

  holiday_hash.each do |seasons, holidays|

    holidays.each do |holidays, supplies|
      puts "#{seasons.to_s.capitalize}:"
      puts "  #{holidays.to_s.tr("_"," ").capitalize}: #{supplies.join(", ")}"
    end

  end

end

all_supplies_in_holidays(holiday_dec)

str.split('_').map(&:capitalize).join(' ')

"fourth_of_july".split('_') -> ["fourth", "of", "july"]
["fourth", "of", "july"].map(&:capitalize) -> ["Fourth", "Of", "July"]
["Fourth", "Of", "July"].join(' ') -> "Fourth Of July"

'fourth_of_july'.titleize => "Fourth Of July"

holiday_dec.each_with_object({}) { |(k,v),h|
  h[k] = v.each_with_object({}) { |(kk,vv),g|
    g[kk.to_s.split('_').map { |s| s[0]=s[0].upcase; s }.join(' ')] = vv } }
  #=> {:winter=>{"Christmas"=>["Lights", "Wreath"], "New Years"=>["Party Hats"]},
  #    :summer=>{"Fourth Of July"=>["Fireworks", "BBQ"]},
  #    :fall=>{"Thanksgiving"=>["Turkey"]},
  #    :spring=>{"Memorial Day"=>["BBQ"]}}

def key_changer hash
  hash.map do |k,v|
    [ k.to_s.scan(/[a-zA-Z]+/).map(&:capitalize).join(' '),
      v.class == Hash ? key_changer(v) : v ]
  end.to_h
end

key_changer holiday_dec #=>

#{ "Winter" => { "Christmas"      => ["Lights", "Wreath"],
#                "New Years"      => ["Party Hats"] },
#  "Summer" => { "Fourth Of July" => ["Fireworks", "BBQ"] },
#  "Fall"   => { "Thanksgiving"   => ["Turkey"] },
#  "Spring" => { "Memorial Day"   => ["BBQ"]}
#}

irb> 'some_class_string'.classify
=> "SomeClassString"