Hi Guys
Over the past week (well, since RailsConf finished) I’ve been working
on a Ruby Specifications library called ActiveSpec, with the aim to
provide an alternative to Rails validations module (though ActiveSpec
can be used outside of Rails apps too).
What is ActiveSpec?
It is an implementation of the Specification domain pattern. ActiveSpec
provides built-in low-level specification classes (that mostly mirror
Rails’ validates_* macros) and a few extras like composite specs and a
spec negator decorator. It provides a more declarative way of creating
composite specs, with the ActiveSpec::Base class, and finally it
provides a high-level DSL for creating specifications. What does that
DSL look like?
specification :user do
should_require_presence_of :username, :password
should_require_confirmation_of :password
end
You can also do a form of specification inheritance:
specification :authenticated_user do
should_satisfy :user_specification # the above spec
end
You can even uses Ruby procs for quick, arbitrary specs:
specification :foo do
should_satisfy { |obj| # do something }
end
Finally there is the Satisfies module which makes attaching specs
directly to your classes (including ActiveRecord classes), a breeze:
ActiveRecord::Base.send(:include, ActiveSpec::Satisfies)
class User < ActiveRecord::Base
should_satisfy :user_specification
should_satisfy :activated_user_specification, :if => :activated?
end
Why ActiveSpec?
Rails’ validates_* macros are awesome but sometimes you want a bit more
power, and using the lower level validate methods is a bit icky. More
importantly, as we found out on a recent project with a particularly
complex domain model, you sometimes want to validate your model in
different ways depending on its state or what context it is being used
in. Its hard to do this elegantly with Rails’ current validations API.
Is it ready to use?
Not quite, but theres enough there to check out and start playing with.
The major thing that it is lacking that Rails validations have, is
error messages. This will be added but I haven’t tackled it yet. But
I’d love people to check out the trunk and have a play and provide me
with some feedback at this early stage.
Where can I find it?
You can grab the source code from the Agile Evolved open source
repository:
http://opensource.agileevolved.com/svn/root/activespec/trunk/
You can check out the RDocs here:
http://docs.britsonrails.org.uk/activespec/
I’ve tried to fully document the API as best as I can. There’s also a
README file there with more information.
License?
MIT, natch!
Have fun, let me know how you get on!
(by the way, if you want to know more about the Specification pattern
beyond what google tells you, I cannot recommend Domain Driven Design
by Eric Evans enough!).
