Active Record validations are a well-known and widely used in Rails.
class User < ApplicationRecord validates :name, presence: { message: "must be given please" } end This runs the validation on save, both when creating a new record or when updating an existing record.
on option allows control over when to run the validation, commonly used with value of create or update
class User < ApplicationRecord belongs_to :club, optional: true validates :name, presence: { message: "must be given please" }, on: :create validates :club, presence: { message: "must be given please" }, on: :update end This allows creating users without associating them with a Club, but enforces presence of Club on subsequent updates. This pattern is commonly used to allow users to signup with bare minimum form fields and then forcing them to update their profiles with more information on subsequent visits.
Value for the on option is not limited to create and update, we can have our own custom contexts. Like in a multistep form, we can have validations for each of the steps. on options makes this really easy to do
class User < ApplicationRecord validate :basic_info, on: :basic_info validate :education_details, on: :education_details validate :professional_info, on: :professional_info private def basic_info # Validation for basic info, first_name, last_name, email end def education_details # Validation for education_details end def professional_info # Validation for professional_info end end In the controller
class UsersController < ApplicationController ... def update_basic_info @user.assign_attributes(basic_info_params) @user.save(:basic_info) end def update_education_details @user.assign_attributes(education_details_params) @user.save(:education_details) end def update_professional_info @user.assign_attributes(professional_info_params) @user.save(:professional_info) end private def basic_info_params # strong params end def education_details_params # strong params end def professional_info_params # strong params end end With Rails 5 adding support for multiple contexts, we can use multiple context together
@user.save(:basic_info, :professional_info) This seems pretty neat, let's go a step further and do this with update_attributes. In current implementation of Rails,
update_attributes does not support validation contexts. We can get around this by defining our own custom method
class ApplicationRecord < ActiveRecord::Base self.abstract_class = true def update_attibutes_with_context(attributes, *contexts) with_transaction_returning_status do assign_attributes(attributes) save(context: contexts) end end end In the controller
@user.update_attibutes_with_context({first_name: 'fname'}, :basic_info) Lastly, we can use with_options to group multiple validation within a context
with_options on: :member do |member_user| member_user.validates :club_name, presence: true member_user.validates :membership_id, presence: true end This makes really easy to write readable and maintainable code, with a good separation of concerns.
Read my last post on ActiveRecord Validations here https://dev.to/spidergears/rails-active-record-validation-messages-4dcf
Top comments (2)
Thanks for the article!
I have not used
onoption with custom context, it is interesting approach. But I think it should be used very rarely, because of otherwise we are about to get bloated models with many responsibilities. In most cases such a things would be better to incapsulate out of models, e.g. by using form objects..Absolutely agree with you, should be used only when it fits the case.
Example is for demonstration and to hint at capabilities of the framework, form object are much more suitable for the scenario.
Thanks for going through, and putting out your thoughts. :)