Fact Checker 
Simple ruby gem to define and check hierarchically dependent "facts" about objects.
Synopsys
class Person
include FactChecker
define_fact(:good_job) { p.job.good? }
define_fact(:good_family) { p.family.good? }
define_fact(:is_healthy) { p.health.good? }
define_fact(:is_happy => [:is_healthy, :good_family, :good_job]) { ! p.too_clever? }
...
end
p = Person.new(job: good_job, family: good_family, health: :good, intellect: :too_clever)
p.good_job? # => true
p.good_family? # => true
p.is_healthy? # => true
p.is_happy.available? # => true (dependency satisfied)
p.is_happy? # => falseDescription
The gem is most usefull when you have something like a checklist, a list of tasks that your users should complete to achieve some goal.
For example, let's say that in order to publish an article a user has to:
- write the article
- name the article (user may complete steps 1 & 2 in any order)
- choose its category
- assign tags to the article (user may complete steps 3 & 4 in any order, but only after steps 1 & 2)
- mark article as "ready for review" (only after steps 1-3 are completed, but step 4 is not required)
- recieve approvement from one of moderators (all steps 1-5 are required)
Using fact_checker that logic could be implemented like this:
include FactChecker
define_fact(:step1) { content.present? }
define_fact(:step2) { name.present? }
define_fact(:step3 => [:step1, :step2]) { category.present? }
define_fact(:step4 => [:step1, :step2]) { tag_list.present? }
define_fact(:step5 => :step3) { ready_for_approvement? }
define_fact(:step6 => [:step4, :step5]) { approved? }
def state_of(step)
return 'completed' if public_send(step).valid?
return 'ready_for_action' if public_send(step).available?
return 'not_available'
endJust to compare, a possible alternative implimentation without fact_checker:
def step1_available?
true
end
def step1_valid?
content.present?
end
def step2_available?
true
end
def step2_valid?
name.present?
end
def step3_available?
step1? && step2?
end
def step3_valid?
step3_available? && a.category.present?
end
def step4_available?
step1? && step2?
end
def step4_valid?
step4_available? && tag_list.present?
end
def step5_available?
step3
end
def step5_valid?
step5_available? && a.ready_for_approvement?
end
def step6_available?
step4? && step5
end
def step6_valid?
step6_available? && a.approved?
end
def state_of(step)
return 'completed' if self.public_send(step + '_valid?')
return 'ready_for_action' if self.public_send(step + '_available?')
return 'not_available'
endInstallation
gem install fact_checker