Tip #4 - Validating an Email Address with Ruby on Rails
Did you know that Rails has inbuilt a strong email handling library called (ahem) TMail? I just so happen to maintain this now (Minero Aoki wrote it), but it gives you a great way to validate email addresses…
Update
Rails 3.0 uses Mail now instead of TMail, here is another simple way to validate an email.
Original Post:
If you have ever tried to handle the validation of email addresses in your Rails app, you have probably ended up trying to use something like this to validate the address:
validates_format_of :email,
:with => /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i
Now, this works… in most cases, but there are a few specifics that won’t.
So some of you out there decide that you want a REAL email validation process and so you go for this regular expression instead:
EmailAddress = begin
qtext = '[^\\x0d\\x22\\x5c\\x80-\\xff]'
dtext = '[^\\x0d\\x5b-\\x5d\\x80-\\xff]'
atom = '[^\\x00-\\x20\\x22\\x28\\x29\\x2c\\x2e\\x3a-' +
'\\x3c\\x3e\\x40\\x5b-\\x5d\\x7f-\\xff]+'
quoted_pair = '\\x5c[\\x00-\\x7f]'
domain_literal = "\\x5b(?:#{dtext}|#{quoted_pair})*\\x5d"
quoted_string = "\\x22(?:#{qtext}|#{quoted_pair})*\\x22"
domain_ref = atom
sub_domain = "(?:#{domain_ref}|#{domain_literal})"
word = "(?:#{atom}|#{quoted_string})"
domain = "#{sub_domain}(?:\\x2e#{sub_domain})*"
local_part = "#{word}(?:\\x2e#{word})*"
addr_spec = "#{local_part}\\x40#{domain}"
pattern = /\A#{addr_spec}\z/
end
And then your validates_format_of becomes:
validates_format_of :email,
:with => EmailAddress
Which is neat, but you have to stuff that Regex away somewhere. When I used this, (by the way) I would make a file in /lib called ‘rfc822.rb’ and then put this in it:
#
# RFC822 Email Address Regex
# --------------------------
#
# Originally written by Cal Henderson
# c.f. http://iamcal.com/publish/articles/php/parsing_email/
#
# Translated to Ruby by Tim Fletcher, with changes suggested by Dan Kubb.
#
# Licensed under a Creative Commons Attribution-ShareAlike 2.5 License
# http://creativecommons.org/licenses/by-sa/2.5/
#
module RFC822
EmailAddress = begin
qtext = '[^\\x0d\\x22\\x5c\\x80-\\xff]'
dtext = '[^\\x0d\\x5b-\\x5d\\x80-\\xff]'
atom = '[^\\x00-\\x20\\x22\\x28\\x29\\x2c\\x2e\\x3a-' +
'\\x3c\\x3e\\x40\\x5b-\\x5d\\x7f-\\xff]+'
quoted_pair = '\\x5c[\\x00-\\x7f]'
domain_literal = "\\x5b(?:#{dtext}|#{quoted_pair})*\\x5d"
quoted_string = "\\x22(?:#{qtext}|#{quoted_pair})*\\x22"
domain_ref = atom
sub_domain = "(?:#{domain_ref}|#{domain_literal})"
word = "(?:#{atom}|#{quoted_string})"
domain = "#{sub_domain}(?:\\x2e#{sub_domain})*"
local_part = "#{word}(?:\\x2e#{word})*"
addr_spec = "#{local_part}\\x40#{domain}"
pattern = /\A#{addr_spec}\z/
end
end
And then in my model:
include RFC822
validates_format_of :email,
:with => EmailAddress
Which is getting better. But the problem with that now is that you need to maintain that email address regular expression… which is quite… umm… “complex” I think is a good word :)
Enter TMail!
TMail has an “Address” class. It will throw an invalid address exception if given an address it can’t handle (and it has about 2,000 test cases of email addresses it can handle, so you are pretty safe.)
Plus, as the maintainer, whenever I find a valid email that TMail can not handle, I fix it, and then you benefit at the next gem install tmail… so it all turns out good :)
To use it, dump this in your user model somewhere (assuming your user model has the attribute ‘email_address’)
def valid_email?
TMail::Address.parse(email)
rescue
errors.add_to_base("Must be a valid email")
end
Then your validates_format_of becomes:
validate :valid_email?
Which is even nicer.. as in… less code == nicer :)
Next tip => How to validate the address fully before accepting it…
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