dm-fuzz is a bunch of rich property types for DataMapper, which provide semantic wrappers around the built-in primitive types. Rather than declaring a weight property as a Float, define it as a DataMapper::Fuzz::Weight – the added semantic information will provide all kinds of opportunities for validation, sanity checking, implicit unit conversion, and fuzzy parsing… which mostly haven’t been implemented yet.

Um, an example would probably work better.

# the following model is defined in spec/models/child.rb,
# and we'll use it here to demonstrate dm-fuzz in irb

class Child
  include DataMapper::Resource
  include DataMapper::Fuzz

  property :id, Integer, :serial=>true
  property :name, String
  property :gender, Gender
  property :weight, Weight, :unit=>:kg
  property :dob, Age
end

# and since Date#inspect is so utterly useless,
# let's replace that, so we can read the output

class Date
	def inspect
		"#<%s: %s>" % [self.class, to_s]
	end
end

An imaginary IRB session follows…

# create a new Child object. nothing surprising here;
# this is exactly the same as vanilla datamapper

>> Child.new(:name=>"Adam", :gender=>:male, :weight=>80)
=> #<Child id=nil name="Adam" gender=:male weight=80.0 age=nil>

# now, let's set some of those fields with fuzzy data,
# as might be received over SMS or a web form. the kind
# of data that {health extension workers in rural Africa}[http://www.youtube.com/results?search_query=RapidSMS]
# might give you, if you weren't explicit...

>> Child.new(:name=>"Bob", :gender=>"boy", :weight=>"135lb")
=> #<Child id=nil name="Bob" gender=:male weight=61.23496995>

>> Child.new(:gender=>"woman", :age=>"2 years old", :weight=>"8 stones")
=> #<Child id=nil name=nil gender=:female weight=50.80234544 age=#<Date: 2007-03-31>>

>> Child.new(:age=>"1 months", :gender=>"unknown", :weight=>"really fat")
=> #<Child id=nil name=nil gender=nil weight=nil age=#<Date: 2009-02-28>>

# a single arbitrary string can be parsed to
# populate a model's "fuzzable" properties,
# too! this is a bit quirky, right now...

>> a = Child.parse("21 month old female, 15lb")
=> #<Child id=nil name=nil gender=:female weight=6.80388555 age=#<Date: 4908581/2,0,2299161>>

>> b = Child.parse("2 year old boy")
=> #<Child id=nil name=nil gender=:male weight=nil age=#<Date: 4908381/2,0,2299161>>

>> c = Child.parse("woman of 60kg")
=> #<Child id=nil name=nil gender=:female weight=60.0 age=nil>

More coming soon. Don’t use this for anything serious yet, but it’s a rather fun toy.