Using Rails concerns for validation in models

Question

This is my first Rails project. I have read about concerns which are a great tool, but I am confused about how I should redesign my models.

Some models have similar fields, but the validations are not the same everywhere. For example: 3 models have a phone field, but in one model the phone field is not required. 3 models have a name field, but the Partner model doesn't. I am not sure about how I should organize my code.

Models

Event

class Event < ActiveRecord::Base
 include NameFormField, PhoneFormField, LocaleFormField
 include SetUserAssociation, SetCountyAssociation
 belongs_to :school
 validates :phone, presence: true
 validates :description, presence: true 
 validates :event_start, presence: true
 validates :event_end, presence: true
end

Partner

class Partner < ActiveRecord::Base
 include PhoneFormField
 include SetUserAssociation, SetCountyAssociation
 belongs_to :partner_type, class_name: 'Common::PartnerType'
 belongs_to :dance_level, class_name: 'Common::DanceLevel'
 belongs_to :dance_style, class_name: 'Common::DanceStyle'
 belongs_to :dance_goal, class_name: 'Common::DanceGoal'
 validates :email, presence: true
 validates :city, presence: true
 validates :dance_style, presence: true
 validates :dance_level, presence: true
 validates :dance_goal, presence: true
 validates :age, numericality: { less_than_or_equal_to: 120, only_integer: true }
 validates :height, numericality: { less_than_or_equal_to: 300, only_integer: true }, allow_blank: true
 validates :weight, numericality: { less_than_or_equal_to: 100, only_integer: true }, allow_blank: true
 validates :club, length: { maximum: 100, too_long: "%{count} characters are allowed." }, allow_blank: true
 validates :weekly, numericality: { less_than_or_equal_to: 7, greater_than_or_equal_to: 1, only_integer: true }, allow_blank: true
 validates :occasionally,numericality: { less_than_or_equal_to: 5, greater_than_or_equal_to: 1, only_integer: true }, allow_blank: true
 validates :years, numericality: { less_than_or_equal_to: 50, greater_than_or_equal_to: 0, only_integer: true }, allow_blank: true
end

School

class School < ActiveRecord::Base
 include NameFormField, PhoneFormField, LocaleFormField
 include SetUserAssociation, SetCountyAssociation
 has_many :schools_dance_styles, class_name: 'Common::SchoolsDanceStyle'
 has_many :dance_styles, dependent: :destroy, through: :schools_dance_styles, class_name: 'Common::DanceStyle'
 validates :phone, presence: true
 validates :dance_styles,presence: true
 validates :description, presence: true
end

School Review:

class SchoolReview < ActiveRecord::Base
 include NameFormField, SetUserAssociation
 belongs_to :school
 validates :description, presence: true 
 validates :rate, presence: true, numericality: { less_than_or_equal_to: 5, greater_than_or_equal_to: 1, only_integer: true }
end

Concerns:

module NameFormField
 extend ActiveSupport::Concern
 included do
 validates :name, presence: true
 end
end
module PhoneFormField
 extend ActiveSupport::Concern
 included do
 validates :phone, length: { maximum: 20, too_long: "%{count} characters are allowed"} 
 end
 def phone=(value)
 super(value.blank? ? nil : value.gsub(/\D/, '')) 
 end
end
module LocaleFormField
 extend ActiveSupport::Concern
 included do
 validates :city, presence: true
 validates :address, presence: true
 end
end
module SetCountyAssociation
 extend ActiveSupport::Concern
 included do
 belongs_to :county, class_name: 'Common::County'
 validates :county, presence: true
 end
end
module SetUserAssociation
 extend ActiveSupport::Concern
 included do
 belongs_to :user
 validates :user, presence: true
 end
end
module SetSchoolAssociation
 extend ActiveSupport::Concern
 included do
 belongs_to :school
 validates :school, presence: true
 end
end

Can you give me advice about how to organize my code? It seems all models can inherit from a "UserBased" model, because all models need a belongs_to relationship to the User model.

Here an "UML" diagram. The red means actual field is required! (For example in the Partner the phone and description are not required!) enter image description here

• Flambino: Could you add a high-level overview of your models? I.e. what belongs to what. Seems to me that you have quite a few models, and making heads and tails of it from code alone isn't super easy without some basic introduction
• Bóta László: Okay Flambino, just gives me 12 hours :)
• Flambino: No rush :) I just think your question deserves an answer/review, but with a big project it's a little daunting for reviewers to just jump in, so the easier it is to get going, the better
• Bóta László: I've done an "UML" diagram, so you can see what belongs to what. (And the required fields too, those are highlighted with red color.)

Answer 1

To be honest, simple validations like this are not good candidates for concerns because of the additional level of indirection introduced by the concerns themselves. Go for clarity in this case rather than cleverness. Concerns are "clever" in most cases, meaning they are more than what you really need. For your use case, I think concerns are like hitting a thumbtack with a sledge hammer.

• Bóta László: Honestly, I agree with you. I started to refactor this part and many concerns were dropped out.
• janos: @BótaLászló if you like this answer, perhaps you can give it a vote ;-)