Intro to DSLs - Part 3 Answer

gistfile1.rb

# lib/part_3/advanced_credit_score.rb
require_relative 'advanced_consumer'

class AdvancedCreditScore

  def self.simulate(&block)
    consumer = AdvancedConsumer.new

    # TODO Part 3
    # Once again, use instance eval to invoke the block on the consumer
    consumer.instance_eval(&block)

    consumer.score
  end
end

# lib/part_3/advanced_consumer.rb
require_relative 'monthly_score'

class AdvancedConsumer

  attr_reader :accounts, :score

  def initialize
    @score = 0
    @accounts = []
    @months = {}
  end

  def add_account(name)
    # TODO Part 3
    # Add the account name to the accounts array
    @accounts << name
  end

  def month(name, &actions)
    # TODO Part 3
    # Store the block, as a proc, into the months hash, where the key is
    # the name of the account, and the value is the proc
    @months[name] = actions
  end

  # now calculate each month's score
  def score
    @months.each_pair do |name, actions|
      @score += MonthlyScore.new(accounts).process(actions)
    end
    @score
  end
end

# lib/part_3/monthly_score.rb
class MonthlyScore

  attr_reader :paid_balances

  def initialize(accounts)
    # keep track of which accounts are paid
    @paid_balances = {}
    accounts.each do |account|
      @paid_balances[account.to_sym] = 0
    end
  end

  # iterate over all the paid balances and calculate the monthly score
  def calculate_score
    score = 0
    paid_balances.each_pair do |account, value|
      score += (value > 0 ? 1 : -2)
    end
    score
  end

  def pay_bill(account_name, amount)
    paid_balances[account_name.to_sym] = amount
  end

  def process(actions)
    # TODO part 3
    # Convert the actions proc back to a block and use instance eval to
    # execute it in the context of this object
    #
    # Finally, after all the bills have been paid, tally up the score
    # for the month using calculate_score
    instance_eval(&actions)

    calculate_score
  end
end