The Fluent Interface

fluent.rb

# This is an example of the the Fluent Interface Pattern

class ShoppingCart
  attr_reader :items

  def initialize
    @items = []
  end

  def add_item(item)
    @items << item
    self
  end

  def remove_item(item)
    @items.delete_if { |item| item[:name] == item_name }
    self
  end

  def clear
    @items.clear
    self
  end

  def apply_discount(discount)
    @items.each do |item|
      item[:price] -= item[:price] * discount
    end
    self
  end

  def total
    @items.sum { |item| item[:price] }
  end
end

# Example usage:
cart = ShoppingCart.new
cart.add_item({ name: 'Book', price: 12.99 })
  .add_item({ name: 'Pen', price: 1.99 })
  .apply_discount(0.1) # 10% discount
  .remove_item('Pen')

puts "Total: $#{cart.total}" # Total: $11.69