Validate: Only letters, numbers and -

Question

I would like to validate my users, so they can only use a-z and - in their username.

validates_format_of :username, :with => /[a-z]/

However this rule also allows spaces ._@

Username should use only letters, numbers, spaces, and .-_@ please.

Any ideas?

Best regards. Asbjørn Morell

Answer 1

More complex solution but reusable and with more fine grained error messaging.

Custom validator:

app/validators/username_convention_validator.rb

class UsernameConventionValidator < ActiveModel::EachValidator
  def validate_each(record, field, value)
    unless value.blank?
      record.errors[field] << "is not alphanumeric (letters, numbers, underscores or periods)" unless value =~ /^[[:alnum:]._-]+$/
      record.errors[field] << "should start with a letter" unless value[0] =~ /[A-Za-z]/
      record.errors[field] << "contains illegal characters" unless value.ascii_only?
    end
  end
end

(Notice it does allow ' . - _ ' and doesnt allow non ascii, for completeness sake)

Usage:

app/models/user.rb

validates :name,
    :presence => true,
    :uniqueness => true,
    :username_convention => true