Regex to check alphanumeric string in ruby

Question

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-z

Answer 1

def alpha_numeric?(char)  

   if((char =~ /[[:alpha:]]) || (char =~ [[:digits:]]))
      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 helps.

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

Answer 2

No regex:

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

Answer 3

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.

Answer 4

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

Answer 5

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

Answer 6

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.