Ruby编程错误（未定义的局部变量）

Question

我试图制作信用卡付款计算器。这是完整的代码：

m_counter = 0

def calc_payment
  payment_percentage = payment / balance * 100
  monthly_apr = apr / 12
  while balance > 0
   m_counter = m_counter + 1
   balance = balance / 100 * monthly_apr
   balance = balance - payment
  end
  puts
  puts "Monthly payment: $" + payment
  puts "Balance payoff: " + m_counter + " months" 
end

puts "Welcome to your credit card payment calculator!"
puts

puts "Please tell me your credit card balance."
balance = gets.chomp.to_f

puts "Please enter your interest rate %."
apr = gets.chomp.to_f

puts "How much $ would you like to pay every month?"
payment = gets.chomp.to_f

calc_payment

我收到一条错误消息：

  

'calc_payment'：主要的未定义局部变量或方法'payment'：Object（NameError）

Answer 1

您的问题围绕变量范围。 payment具有本地范围，因此函数calc_payment无法“看到”它。在这里，我修改了您的程序，以便将payment，balance和apr传递到calc_payment函数中。我也将m_counter移到了函数中。

def calc_payment(payment, balance, apr)
  m_counter = 0
  payment_percentage = payment / balance * 100
  monthly_apr = apr / 12

  while balance > 0
   m_counter = m_counter + 1
   balance = balance / 100 * monthly_apr
   balance = balance - payment
  end

  puts
  puts "Monthly payment: $" + payment
  puts "Balance payoff: " + m_counter + " months" 

end

puts "Welcome to your credit card payment calculator!"
puts

puts "Please tell me your credit card balance."
balance = gets.chomp.to_f

puts "Please enter your interest rate %."
apr = gets.chomp.to_f

puts "How much $ would you like to pay every month?"
payment = gets.chomp.to_f

calc_payment(payment, balance, apr)