Rails custom validation based on a regex?

Question

I have the following regex that I use in my routes.rb for /type-in-something-here

# A-Z, a-z, 0-9, _ in the middle but never starting or ending in a _
# At l         


        

Answer 1

using something like this

validates :uuid, :format => {:with => /[A-Za-z\d]([-\w]{,498}[A-Za-z\d])?/i},
                 :message => "your message"

For more check this

Answer 2

validates :name, format: { with: /\A[a-zA-Z]+\z/,
message: "Only letters are allowed" }

Answer 3

For validation purposes, remember to add the beginning and end of string markers \A and \Z:

validates_format_of :uuid, :with => /\A[A-Za-z\d]([-\w]{,498}[A-Za-z\d])?\Z/i

Otherwise your regex will happily match any string that contains at least a letter or a digit. For some reason Rails implicitly adds the boundaries in the routes. (Probably because it embeds the regex inside a larger one to match the entire URL, with explicit checks for / and the end of the URL.)