yield_example.rb

class Loan
  attr_accessor :outstanding_balance, :remaining_months, :monthly_repayments

  def save! 
  end
end

def some_calculation
  10
end

def make_change(loan:, &block)
  yield loan if block_given?

  loan.monthly_repayments = some_calculation
  loan.save
end

new_loan = Loan.new

make_change(loan: new_loan) do |yielded_loan|
  yielded_loan.outstanding_balance = 100_00
end

make_change(loan: new_loan) do |yielded_loan|
  yielded_loan.remaining_months = 100
end