This gem provides a shorthand DSL for including re-usable sets of mixin modules across a large set of STI models. If you find yourself with a folder of subclasses full of boilerplate and shared functionality, this gem will let you replace those files with one or a few small files that read more descriptively, like so:
MySuperClass.describe_descendants_with(MySuperClassMixins) do
type :some_type
type :another_subtype do
email_addressable
end
type :some_domain_event do
email_addressable
payment_validatable
end
end
My blog post describes the evolution of this gem at Hired pretty well.
TL;DR imagine the example in the usage section with a marketplace's domain described therein.
Add this line to your application's Gemfile:
gem 'descendants_describable'
And then execute:
$ bundle
Or install it yourself as:
$ gem install descendants_describable
Here's the real-world example that gave life to this gem:
# config/initializers/activities.rb
Activity.describe_descendants_with(Activity::Descriptors) do
type :completed_survey do
user_required
end
type :bid_on_developer do
approved_employers_only
target_required
end
type :auction_membership_confirmed do
approved_developers_only
actor_unique_to_auction
target_required
end
# ... others omitted for brevity ...
end
Given this example, one is describing the descendants of an Activity class (that also live on the activities table with a type column for STI), the following is happening.
- Each "type" declaration instantiates a new subclass by that name camelized.
- Each method called inside the block provided to a "type" declaration will include into that new subclass a module by that method name camelized in the provided descriptor namespace.
So the above is basically shorthand for this:
# in models/completed_survey.rb
class CompletedSurvey < Activity
include Activity::Descriptors::UserRequired
end
# in models/bid_on_developer.rb
class BidOnDeveloper < Activity
include Activity::Descriptors::ApprovedEmployersOnly
include Activity::Descriptors::TargetRequired
end
# in models/auction_membership_confirmed.rb
class AuctionMembershipConfirmed < Activity
include Activity::Descriptors::ApprovedEmployersOnly
include Activity::Descriptors::ActorUniqueToAuction
include Activity::Descriptors::TargetRequired
end
You should put any calls to describe_descendants_with
somewhere where it will only be executed
once per boot of your app (including code reloading), such as an initializer(s). This is because
each time you call describe_descendants_with
, a hook is registered with Rails via
ActiveSupport::Reloader.to_run
; you don't want to register duplicate reload hooks.
- Fork it
- Create your feature branch (
git checkout -b my-new-feature
) - Commit your changes (
git commit -am 'Add some feature'
) - Push to the branch (
git push origin my-new-feature
) - Create new Pull Request