CODEWITHSUNDEEP
rubyuser-input
Taj
Taj

Reputation: 107

How do I check if user input is an integer in Ruby?

I am trying to loop until user inputs an integer. When user inputs a letter, the following code should print "Think of a number":

print "Think of a number "

while user_input = gets.to_i
  if user_input.is_a? Integer
    puts "your number is #{user_input}"
    break
  else
    print "Think of a number "
  end 
end

I succeeded with my code when user inputs an integer. However when user inputs a string, the to_i method returns 0, and does not execute the else statement because it is a number.

Upvotes: 1

Views: 2221

Answers (4)

Oli Crt
Oli Crt

Reputation: 1173

If you only want to accept postive digits, you can use a range:

user_input = gets.chomp 
if ('0'..'9').cover? user_input

Upvotes: 2

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121000

The main issue with your code is String#to_i method is omnivorous.

"0".to_i #⇒ 0
"0.1".to_i #⇒ 0
"foo".to_i #⇒ 0

That said, user_input in your code is always integer.

What you probably want is to accept digits only (and maybe a leading minus for negatives.) The only concise way to accept a subset of characters is a regular expression.

# chomp to strip out trailing carriage return
user_input = gets.chomp 

if user_input =~ /\A-?\d+\z/
  ...

The regular expression above means nothing save for digits with optional leading minus.

Or, even better (credits to @Stefan)

if gets =~ /\A-?\d+\Z/

Upvotes: 4

Vaibhav
Vaibhav

Reputation: 658

I came across a similar problem. I ended up doing this: 

if user_input.strip == user_input.to_i.to_s
  # More code here!
end

Testing for float would be: 

if user_input.strip == user_input.to_f.to_s
  # More code here!
end

Solved my issue. See if it helps.

Upvotes: -1

rahul mishra
rahul mishra

Reputation: 1470

let check below one used Integer(gets.chomp) rescue ''

print "Think of a number "

while user_input = Integer(gets.chomp) rescue ''
  if user_input.is_a? Integer
    puts "your number is #{user_input}"
    break
  else
    print "Think of a number "
  end
end

Upvotes: 0

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