Question

I would like my User model to sanitize some input before before save. For now some simple whitespace stripping will do.
So to avoid people registering with “Harry ” and pretend to be “Harry”, for example.

I assume it is a good idea to do this stripping before validation, so that the validates_uniqueness_of can avoid accidental duplicates.

class User < ActiveRecord::Base
  has_many :open_ids

  validates_presence_of :name
  validates_presence_of :email
  validates_uniqueness_of :name
  validates_uniqueness_of :email
  validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i

  before_validation :strip_whitespace, :only => [:name, :email, :nick]

  private
  def strip_whitespace(value)
    value.responds_to?('strip') ? value.strip : value
  end
end

However, this code comes with an error ArgumentError: wrong number of arguments (0 for 1). I assumed the callback would be passed the values.

Also: is this stripping actually a good idea? Or should I rather validate on space and tell the user that “Harry ” contains invalid spacess (I want to allow “Harry Potter” but not “Harry\s\sPotter”).

Edit: As pointed out in a comment, my code is wrong (which is why I was asking the question a.o.). Please make sure you read the accepted answer in addition to my question for the correct code and to avoid the same mistakes I made.

Answer 1

I don’t believe before_validation works like that. You probably want to write your method like this instead:

def strip_whitespace
  self.name = self.name.strip unless self.name.nil?
  self.email = self.email.strip unless self.email.nil?
  self.nick = self.nick.strip unless self.nick.nil?
end

You could make it more dynamic if you want using something like self.columns, but that’s the gist of it.