Ruby (and Rails) attribute cleaning upon write, provides some nice default normalization strategies.
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Vacuum Cleaner

A Ruby (and Rails) attribute normalization gem.

Note: Starting with Version 2.0.0 it is no longer compatible with Rails 2.x, please use 1.x.


Add this line to your application's Gemfile:

gem 'mote_sms'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mote_sms


It creates a new setter method for an attribute and thus allows the normalizers defined to reprocess the input value.

class Doctor
  include VacuumCleaner::Normalizations  # enables #normalizes, NOTE: not required for ActiveRecord models
  attr_accessor :name                    # create some reader/writter

  normalizes :name                       # enables strip/clean-up magic on attribute :name

Using normalizes just adds a default normalization implemenation, which removes leading/trailing whitespace and converts spaces only to nil. Everything happens upon "set".

@doc = = "  Elliot Reid\n\t"   # => "Elliot Reid" => trailing space was stripped = "\t\n"   # => nil => converted to nil

Okay, this is how it basically works, the normalizes call just generates a new setter method, which normalizes the input value and then calls the original setter method.

What else can be done then?

# can be used with multiple attributes (if they all share the same normalizer)
normalizes :name, :company

# provides a fancy :downcase and :upcase normalizer (guess what they do)
normalizes :email, :downcase => true
# "JD@EXAMPLE.COM \n" => ""

# provides a :method normalizer which takes a string/symbol as argument which is
# then called upon the resulting value (if it respond_to)
normalizes :name, :method => :titleize
# "carla ESPINOSA" => "Carla Espinosa" PS: only works if ActiveSupport is available :)

# or a simple URL normalizer, which prefixes http:// if not starting with
# http or https
normalizes :homepage, :url => true
# "" => ""
# "" => "" PS: left as is

Take a look at VacuumCleaner::Normalizer, about how the process works and how custom reusable normalizers can be written. For the-quick-fix-that-shouldnt-have-been-used-but-was case or if there's no reuse, normalizes takes a block as argument which is called after any other normalizer in the chain. Note that normalizers are not halted, nor stopped if they return nil or false or something similar, so ensure that case is handled properly.

# strips all whitespace within a string
normalizes(:phone) { |value| value.to_s.gsub(/\s+/, '') unless value.nil? }
# "\t+45 123 123  " => "+45123123" PS: yes, the standard strip etc. magic is still run

# no need for the default normalizer and feeling really custom?
normalizes(:phone, :default => false, :upcase => true) { |value| value.to_s.strip.gsub(/\s+/, '') }
# "\t0800 sacred heart" => "0800SACREDHEART"
# "\t\n" => ""
# nil => ""

Need access to the full object within the block? As easy as:

# naming J.D. after some girly girl?
normalizes(:first_name) do |obj, attribute, value| == "Dorian" ? %w{Agnes Shirley Denise}[rand(3)] : value


As mentoined earlier normalizes creates a new setter method, so let's shortly take a look at how.


# 1. creates a :normalize_name method, which contains the normalization chain, block etc.
# 2. if :name= exists, it's aliased to :name_without_normalization=
# 3. creates a new :name= method, which calls :normalize_name, then tries to
#    set the normalized value by one of:
#    a) calling :name_without_normalization=, if defined
#    b) self[:name] = v, if it responds to :[]= (for ActiveRecord support)
#    c) or, as a fallback, sets @name to the result of :normalize_name

Lessons learned: when the need arises to set the value without any normalization and there's a setter just use @object.name_without_normalization = "har har har\n\t". Feel free to completly override normalize_<attribute>, but a much smarter way to add very custom normalizers is by a) providing a block to normalizes or b) create a custom VacuumCleaner::Normalizer implementation.

Some info about the different files, might be a good place to look at when trying to figure out how to write custom VacuumCleaner::Normalizer implemenations, or for a look at how it works.

lib/vacuum_cleaner/normalizer.rb        # Base Normalizer implementation
lib/vacuum_cleaner/normalizations/*.rb  # Some default Normalizer implementations, like url, downcase etc.
lib/vacuum_cleaner/normalizations.rb    # Provides the `normalizes` method and all the logic etc.