Ruby 编程错误（未定义的局部变量）答案

【问题标题】：Ruby programming error (undefined local variable)Ruby 编程错误（未定义的局部变量）
【发布时间】：2013-10-12 14:04:25
【问题描述】：

我尝试制作信用卡付款计算器。这是整个代码：

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

【问题讨论】：

Vori，一个小建议：(payment / balance) * 100 或（更好）100 * payment / balance 而不是payment / balance * 100（更清晰）。此外，您可以使用 puts "hi\n\n" 而不是 puts "hi"; puts; puts（仅风格差异）。

标签： ruby variables syntax-error undefined nameerror

【解决方案1】：

您的问题围绕变量范围展开。 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，以便您将payment、balance 和apr 传递给calc_payment 函数。我还将m_counter 也移到了函数中。

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)

【讨论】：