Need help validating if user input is a number - ruby

Question

I have the following code:
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
I need it to take the num1 and num2 variables that the user inputs and validate that they are numbers and return a message if they aren't.
I would like to use a Regex, but I don't know if I should create a method for this or just wrap it in a loop.

Answer 1

The Integer method will raise an exception when the given string is not a valid number, whereas to_i will fail silently (which I think is not desired behavior):
begin
num = Integer gets.chomp
rescue ArgumentError
say "Invalid number!"
end
If you want a regex solution, this will also work (although I recommend the method above):
num = gets.chomp
unless num =~ /^\d+$/
say "Invalid number!"
end

Answer 2

You would often see each section written something like this:
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)
Here's possible dialog:
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