CODEWITHSUNDEEP
rubyregexvalidation
zensupremacy
zensupremacy

Reputation: 57

Ruby - validate user input against allowed characters

i am stuck at validating user input. i have set of allowed characters "R G B Y" and i am asking for user input. I want to validate if user inputs ONLY characters that are allowed ("R G B Y").

User can input whatever he or she wants as long as input include allowed characters, for example:

user_input1 = "R R R Y"
user_input2 = "Y Y B G"

and so on...

i am totally stuck, i tried with regex:

/[RGBY]/

it is working fine if user inputs allowed characters, but if there will be a mix of allowed and not allowed characters, regex won't catch it :( for example:

wrong_user_input = "Z Z R Y"

i know regex is overkill for this simple task but i cannot think of something else in this moment. any help would be appreciated.... thanks!

Upvotes: 2

Views: 313

Answers (3)

Cary Swoveland
Cary Swoveland

Reputation: 110755

Here are some more ways, some of which do not employ a regex.

Negation of: the string contains a character other than "R", "G", "B", "V" and " "

!('Z Z R Y' =~ /[^RGBY ]/) #=> false
!('R R R Y' =~ /[^RGBY ]/) #=> true

This avoids the need for anchors.

Use String#delete to remove target characters and then see if any characters are left

'Z Z R Y'.delete('RGBY ').empty? #=> false
'R R R Y'.delete('RGBY ').empty? #=> true

One variant of this is to use String#tr:

'Z Z R Y'.tr('RGBY ', '').empty? #=> false
'R R R Y'.tr('RGBY ', '').empty? #=> true

Another is to use String#gsub with a regex:

'Z Z R Y'.gsub(/[RGBY ]/, '').empty? #=> false
'R R R Y'.gsub(/[RGBY ]/, '').empty? #=> true

Convert the string to an array of characters and use a logical comparison

arr = ['R', 'G', 'B', 'Y', ' ']

('Z Z R Y'.chars - arr).empty? #=> false
('R R R Y'.chars - arr).empty? #=> true

Upvotes: 1

Eric Duminil
Eric Duminil

Reputation: 54303

There was a related question a while ago, and this came out as the fastest solution :

"Z Z R Y".count("^RGBY ") == 0
#=> false
"R G R Y".count("^RGBY ") == 0
#=> true

It counts characters that are not R,G,B,Y or space.

Upvotes: 2

falsetru
falsetru

Reputation: 369454

Use /^[RGBY ]+$/ as a pattern, so that from the beginning (^) to the end ($) (not partially) whole characters are consisted of allowed characters (R, G, B, Y, or space):

>> "Z Z R Y" =~ /^[RGBY ]+$/
=> nil
>> "R R R Y" =~ /^[RGBY ]+$/
=> 0

Upvotes: 3

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