Question

我有以下代码：

def say(msg)
  puts "=> #{msg}"
end

def do_math(num1, num2, operation)
  case operation
    when '+'
      num1.to_i + num2.to_i
    when '-'
      num1.to_i - num2.to_i
    when '*'
      num1.to_i * num2.to_i
    when '/'
      num1.to_f / num2.to_f
    end
end

say "Welcome to my calculator!"

run_calculator = 'yes'

while run_calculator == 'yes'
  say "What's the first number?"

  num1 = gets.chomp

  say "What's the second number?"

  num2 = gets.chomp

  say "What would you like to do?"

  say "Enter '+' for Addition, '-' for Subtraction, '*' for Multiplication, or '/' for Division"

  operation = gets.chomp

  if num2.to_f == 0 && operation == '/'
    say "You cannot devide by 0, please enter another value!"
    num2 = gets.chomp
  else
    result = do_math(num1, num2, operation)
  end

  say "#{num1} #{operation} #{num2} = #{result}"

  say "Would you like to do another calculation? Yes / No?"
  run_calculator = gets.chomp

  if run_calculator.downcase == 'no'
    say "Thanks for using my calculator!"
  elsif run_calculator.downcase == 'yes'
    run_calculator = 'yes'
  else
    until run_calculator.downcase == 'yes' || run_calculator.downcase == 'no'
      say "Please enter yes or no!"
      run_calculator = gets.chomp
    end
  end
end

我需要它来获取用户输入的num1和num2个变量并验证它们是数字并返回消息（如果它们不是）。

我想使用正则表达式，但我不知道是否应该为此创建一个方法，或者只是将它包装在一个循环中。

Answer 1

当给定字符串不是有效数字时，Integer方法将引发异常，而to_i将无声地失败（我认为这不是所希望的行为）：

begin
  num = Integer gets.chomp
rescue ArgumentError
  say "Invalid number!"
end

如果你想要一个正则表达式解决方案，这也可行（虽然我推荐上面的方法）：

num = gets.chomp
unless num =~ /^\d+$/
  say "Invalid number!"
end

Answer 2

您经常会看到每个部分都写成这样的内容：

ERR_MSG = "You must enter a non-negative integer"

def enter_non_negative_integer(instruction, error_msg)
  loop do
    puts instruction
    str = gets.strip
    return str.to_i if str =~ /^\d+$/
    puts error_msg
  end
end

x1 = enter_non_negative_integer("What's the first number?", ERR_MSG)
x2 = enter_non_negative_integer("What's the second number?", ERR_MSG)

这是可能的对话：

What's the first number?
: cat
You must enter a non-negative integer
What's the first number?
: 4cat
You must enter a non-negative integer
What's the first number?
:             22
#=> 22
What's the second number?
: 51
#=> 51

x1 #=> 22
x2 #=> 51

如果用户输入是一个数字，需要帮助验证

2 个答案: