Simple regex is not working.. For example first_name = "a11" works fine. Why isn't my format regex validating properly?
validates :first_name, presence: { message: "Name cannot be blank." },
format: { with: /[a-z]/i, message: "Name must only contain letters." },
length: { minimum: 2, message: "Name must be at least 2 letters." }
Because it matches with you regex.
You have to specify the begin and end of the string, and add * or it will just match one char.
format: { with: /\A[a-z]*\z/i, message: "Name must only contain letters." },
Also note don't use ^ and $, in ruby, ^ and $ matches the begin and end of a line, not the string, so it will be broken on multiline strings.
Your regex returns a match. It's looking for any letter that's present anywhere in the string and returns that match. You want to specify that only letters are allowed.
Update Original answer insecure: https://stackoverflow.com/a/17760113/836205
If you change it to /^[a-z]*$//\A[a-z]*\z/ it will only match a string that contains all lower case letters.
The provided regular expression is using multiline anchors (^ or $), which may present a security risk. Did you mean to use \A and \z, or forgot to add the :multiline => true option?
[0-9a]+or[0-9a-z]+