Keep healthy and reduce responsibility of ActiveRecord models
Presenters
Presenters pattern may be more commonly known as the View-Model pattern.
The idea is we want to seperate the code related with presenting and displaying attribute of instance model in View. View != Model. The Model only contains logic code, don’t need to contain code related with View.
We call it a Presenter, it’s just a class represent displaying logic from Model to View.
Presenters can solve problem:
- too much logic code in Views
- large size helpers
- models has view code
Presenters implementation
# defind User model class
class User < ActiveRecord::Base
attr_accessible :last_name, :first_name
end
# define presenter file, app/views/presenters/user.rb
require 'delegate'
class UserPresenter < SimpleDelegator
def full_name
"My name is #{model.first_name} #{model.last_name}"
end
def model
__getobj__
end
end
# in controller
@user = UserPresenter.new(User.new(first_name: "tuan", last_name: "kiet")
# in view
@user.full_name
Concerns
Concerns help reduce logic write in models, remove duplicate function accross models, also grouping code relate of logic together. assume, we have two model which have same methods serve same logic, we can move this code into models/concerns/
class Blog < ActiveRecord::Bas
def long_date
date.strftime("%Y/%M/%d")
end
end
class Comment < ActiveRecord::Base
def long_date
date.strftime("%Y/%M/%d")
end
end
# move long_date into concerns
# app/models/concerns/date_formatable.rb
module Concerns::DateFormattable
def long_date
date.strftime("%Y/%M/%d")
end
end
# inside models we must include Concerns::DateFormattable
class Blog < ActiveRecord::Bas
include Concerns::DateFormattable
end
class Comment < ActiveRecord::Bas
include Concerns::DateFormattable
end
Services
Services are Rails pattern with the aim to keep logic in Controller clearly, can put the logic bussiness in one place, help refactor and testing easier and better. Assume, if you have the logic “after user create successfully, the app sent email confirm and notify for admin known”. So we can create the service class to do job sent email and notify, and in controller you only need call action create user.
class UserController < ApplicationController
def create
@event = UserEventCreate.new.exec(user_params)
end
end
class UserEventCreate
def exec(user_params)
user = User.create(user_params)
if user.valid?
send_email_confirm(user)
notify_admin(user)
end
end
def send_email_confirm(user)
EventMailer.notify(user).deliver
end
def notify_admin(user)
EventMailer.notify_admin(user).deliver)
end
end