CODEWITHSUNDEEP
rubyregexruby-on-rails-3
Mandar Dalvi
Mandar Dalvi

Reputation: 199

Regex to check alphanumeric string in ruby

I am trying to validate strings in ruby. Any string which contains spaces,under scores or any special char should fail validation. The valid string should contain only chars a-zA-Z0-9 My code looks like.

def validate(string)
    regex ="/[^a-zA-Z0-9]$/
    if(string =~ regex)
        return "true"
    else
        return "false"
end

I am getting error: TypeError: type mismatch: String given.

Can anyone please let me know what is the correct way of doing this?

Upvotes: 20

Views: 20600

Answers (8)

Enow B. Mbi
Enow B. Mbi

Reputation: 319

def alpha_numeric?(char)  
 
   if (char =~ /[[:alpha:]]/ || char =~ /[[:digit:]]/)
      true
   else
      false
   end

end

OR

def alpha_numeric?(char)  
 
   if (char =~ /[[:alnum:]]/)
      true
   else
      false
   end

end

We are using regular expressions that match letters & digits:

The above [[:alpha:]] ,[[:digit:]] and [[:alnum:]] are POSIX bracket expressions, and they have the advantage of matching Unicode characters in their category. Hope this helps.

checkout the link below for more options: Ruby: How to find out if a character is a letter or a digit?

Upvotes: 6

user16452228
user16452228

Reputation:

Similar to the very efficient regex-ish approach mentioned already by @steenslag and nearly just as fast:

str.tr("a-zA-Z0-9", "").length.zero?

OR

str.tr("a-zA-Z0-9", "") == 0

One benefit of using tr though is that you could also optionally analyze the results using the same basic formula:

str = "ABCxyz*123$"

rejected_chars = str.tr("a-zA-Z0-9", "")
#=>  *$

is_valid = rejected_chars.length.zero?
#=> false

Upvotes: 1

Joshua Pinter
Joshua Pinter

Reputation: 47481

Use .match? in Ruby 2.4+.

Ruby 2.4 introduced a convenient boolean-returning .match? method.

In your case, I would do something like this:

# Checks for any characters other than letters and numbers.
# Returns true if there are none. Returns false if there are one or more.
#
def valid?( string )
  !string.match?( /[^a-zA-Z0-9]/ ) # NOTE: ^ inside [] set turns it into a negated set.
end

Upvotes: 2

Aaron Washburn
Aaron Washburn

Reputation: 300

Great answers above but just FYI, your error message is because you started your regex with a double quote ". You'll notice you have an odd number (5) of double quotes in your method.

Additionally, it's likely you want to return true and false as values rather than as quoted strings.

Upvotes: 1

Michael Papile
Michael Papile

Reputation: 6856

If you are validating a line:

def validate(string)
  !string.match(/\A[a-zA-Z0-9]*\z/).nil?
end

No need for return on each.

Upvotes: 14

steenslag
steenslag

Reputation: 80065

No regex:

def validate(str)
  str.count("^a-zA-Z0-9").zero?  # ^ means "not"
end

Upvotes: 1

Cary Swoveland
Cary Swoveland

Reputation: 110675

Similar to @rohit89:

VALID_CHARS = [*?a..?z, *?A..?Z, *'0'..'9']
  #=> ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",
  #    "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
  #    "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
  #    "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",
  #    "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]

def all_valid_chars?(str)
  a = str.chars
  a == a & VALID_CHARS
end

all_valid_chars?('a9Z3')  #=> true
all_valid_chars?('a9 Z3') #=> false

Upvotes: 0

rohit89
rohit89

Reputation: 5773

You can just check if a special character is present in the string. 

def validate str
 chars = ('a'..'z').to_a + ('A'..'Z').to_a + (0..9).to_a
 str.chars.detect {|ch| !chars.include?(ch)}.nil?
end

Result:

irb(main):005:0> validate "hello"
=> true
irb(main):006:0> validate "_90 "
=> false

Upvotes: 5

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