Question

I want to create an object, let’s say a Pie.

class Pie 
  def initialize(name, flavor) 
    @name = name 
    @flavor = flavor 
  end 
end

But a Pie can be divided in 8 pieces, a half or just a whole Pie. For the sake of argument, I would like to know how I could give each Pie object a price per 1/8, 1/4 or per whole. I could do this by doing:

class Pie 
  def initialize(name, flavor, price_all, price_half, price_piece) 
    @name = name 
    @flavor = flavor 
    @price_all = price_all
    @price_half = price_half
    @price_piece = price_piece
  end 
end 

But now, if I would create fifteen Pie objects, and I would take out randomly some pieces somewhere by using a method such as

getPieceOfPie(pie_name)

How would I be able to generate the value of all the available pies that are whole and the remaining pieces? Eventually using a method such as:

   myCurrentInventoryHas(pie_name)
   # output: 2 whole strawberry pies and 7 pieces.

I know, I am a Ruby nuby. Thank you for your answers, comments and help!

Answer 1

You’ll definitely want separate Pie and PiePiece classes

class Pie
  attr_accessor :pieces
  def initialize
    self.pieces = []
  end

  def add_piece(flavor)
    raise "Pie cannot have more than 8 pieces!" if pieces.count == 8
    self.pieces << PiePiece.new(flavor)
  end

  # a ruby genius could probably write this better... chime in if you can help
  def inventory
    Hash[pieces.group_by(&:flavor).map{|f,p| [f, p.size]}]
  end

end

class PiePiece
  attr_accessor :flavor
  def initialize(flavor)
    self.flavor = flavor
  end
end

sample code

p = Pie.new
p.add_piece(:strawberry)
p.add_piece(:strawberry)
p.add_piece(:apple)
p.add_piece(:cherry)
p.add_piece(:cherry)
p.add_piece(:cherry)

p.inventory.each_pair do |flavor, count|
  puts "Pieces of #{flavor}: #{count}"
end

# output
# Pieces of strawberry: 2
# Pieces of apple: 1
# Pieces of cherry: 3