Validate multiple contexts together in Rails 5
This blog is part of our Rails 5 series.
Active Record validation is a well-known and widely used functionality of Rails. Slightly lesser popular is Rails’s ability to validate on custom context.
If used properly, contextual validations can result in much cleaner code. To understand validation context, we will take example of a form which is submitted in multiple steps:
class MultiStepForm < ActiveRecord::Base
validate :personal_info
validate :education, on: :create
validate :work_experience, on: :update
validate :final_step, on: :submission
def personal_info
# validation logic goes here..
end
# Smiliary all the validation methods go here.
endLet’s go through all the four validations one-by-one.
1. personal_info validation has
no context defined
(notice the absence of on:).
Validations with no context
are executed every time
a model save is triggered.
Please go through all the triggers
here.
2. education validation has
context of :create.
It is executed only
when a new object is created.
3. work_experience validation
is in :update context
and gets triggered for updates only.
:create and :update
are the only two pre-defined contexts.
4. final_step is validated using
a custom context named :submission.
Unlike above scenarios,
it needs to be
explicitly triggered like this:
form = MultiStepForm.new
# Either
form.valid?(:submission)
# Or
form.save(context: :submission)valid? runs the validation
in given context
and populates errors.
save would first call valid?
in the given context
and persist the changes
if validations pass.
Otherwise populates errors.
One thing to note here is that
when we validate using an explicit context,
Rails bypasses all other contexts
including :create and :update.
Now that we understand validation context, we can switch our focus to validate multiple context together enhancement in Rails 5.
Let’s change our contexts from above example to
class MultiStepForm < ActiveRecord::Base
validate :personal_info, on: :personal_submission
validate :education, on: :education_submission
validate :work_experience, on: :work_ex_submission
validate :final_step, on: :final_submission
def personal_info
# code goes here..
end
# Smiliary all the validation methods go here.
endFor each step, we would want to validate the model with all previous steps and avoid all future steps. Prior to Rails 5, this can be achieved like this:
class MultiStepForm < ActiveRecord::Base
#...
def save_personal_info
self.save if self.valid?(:personal_submission)
end
def save_education
self.save if self.valid?(:personal_submission)
&& self.valid?(:education_submission)
end
def save_work_experience
self.save if self.valid?(:personal_submission)
&& self.valid?(:education_submission)
&& self.valid?(:work_ex_submission)
end
# And so on...
endNotice that
valid? takes only one context
at a time.
So we have to repeatedly
call valid? for each context.
This gets simplified in Rails 5
by enhancing valid? and invalid?
to accept an array.
Our code changes to:
class MultiStepForm < ActiveRecord::Base
#...
def save_personal_info
self.save if self.valid?(:personal_submission)
end
def save_education
self.save if self.valid?([:personal_submission,
:education_submission])
end
def save_work_experience
self.save if self.valid?([:personal_submission,
:education_submission,
:work_ex_submission])
end
endA tad bit cleaner I would say.