How do I use regular expressions in Ruby?

Question

I don't know how to implement regular expressions in Ruby. I tried this code, but it always returns true:

firstName = "Stepen123"
res = Validation_firstName(firstName)
puts res

def  Validation_firstName(firstName)
   reg = /[a-zA-z][^0-9]/
if reg.match(firstName)
   return true 
else
   return false
 end
 end

I am not sure what I did wrong.

Your regex matches a single letter followed by something that is not a digit, so it matched the beginning of your string, specifically "St". What are you trying to match, anyway? — Ray Toal
– Ray Toal, Commented May 9, 2013 at 5:23
Go to rubular.com/r/59cqVn4YPs and use it to see how your pattern works. — the Tin Man
– the Tin Man, Commented May 9, 2013 at 5:26
thank you, i have to match if firstName should have only "Stepen" not "Stepen123", simply "Stepen" returns true, "stepen123" returns false — God
– God, Commented May 9, 2013 at 5:27

the Tin Man · Accepted Answer · 2013-05-09 05:29:21Z

3

You can rewrite your method like this:

def validation_firstname(first_name)
  !!first_name[/^[a-z]+$/i]
end

answered May 9, 2013 at 5:29

the Tin Man

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3 Comments

God Over a year ago

really thankYou its working, i have tried /^[a-zA-Z]$/ this. i havent put "+". whats the meaning for this "+"

Chuck Over a year ago

@God: It means "one or more." So one or more characters in the set [a-zA-Z]. Without that, it will only match one-character strings.

the Tin Man Over a year ago

That is going to be for you to figure out. There are all sorts of regular expression tutorials on the internet, along with the cheat-sheet at the bottom of the page at Rubular.com. I'll just say that without it your code won't work and you should use what I gave in my example, rather than leave out things you don't understand.

Arup Rakshit · Accepted Answer · 2013-05-09 05:50:12Z

1

def validation_firstname(first_name)
  first_name.scan(/\d+/).empty?
end

p validation_firstname("Stepen123") #=> false
p validation_firstname("Stepen") #=> true

answered May 9, 2013 at 5:50

Arup Rakshit

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1 Comment

Chuck Over a year ago

This will return true for the input " ", which I don't think is desired.

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