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· 5 min read · activerecord association polymorphic

Enhance Rails Models

In Rails Models play a important part in our Rails App.We should keep are model pretty,not having dirty code Here i am just reminding you some basic points to refactor a model.

1. Follow law of Demeter(In rails it means use only one dot) {% codeblock lang:ruby%} class Author < ActiveRecord::Base has_many :books has_one :address end class Book < ActiveRecord::Base belongs_to :author end class Address < ActiveRecord::Base belongs_to :author end {% endcodeblock %}

So if in a view we have something like

{% codeblock lang:ruby%} @book.author.name @book.author.address.street @book.author.address.city @book.author.address.state {% endcodeblock %} Here we are calling an object's related object using a third(book -> customer -> address) Luckily in Rails we have Delegate that can escape us from this situation {% codeblock lang:ruby%} class Author < ActiveRecord::Base has_many :books has_one :address end class Book < ActiveRecord::Base belongs_to :author' delegate :name, :street, :city, :state, :to => :author, :prefix => true, :allow_nil => true end class Address < ActiveRecord::Base belongs_to :author delegate :street,:city,:state, :to => :address ,:allow_nil => true end {% endcodeblock %}

So if in a view we have something like

{% codeblock lang:ruby%} @book.author_name @book.author_street @book.author_city @book.author_state {% endcodeblock %}

Now we have just only dot.Here :allow_nil option prevents the error call method on nil object

2. Use callback and validation.instead of writing large code in your method {% codeblock lang:ruby%} class User < ActiveRecord::Base email_confirmation attr_accessor :email_confirmation def user_save if email && email_confirmation && save #send_email end end end {% endcodeblock %} Instead of doing that you can use a call back after_create {% codeblock lang:ruby%} class User < ActiveRecord::Base validates :email, :confirmation => true validates :email_confirmation, :presence => true after_create :send_email private def send_email #send_email end end {% endcodeblock %} So now when you create user it validates if email and email_confirmation attribute is there will send email just after saving the user (here you don't need to define attr_accessor :email_confirmation and don't need to tae attr email_confirmation in db table )

3. Include Modules {% codeblock lang:ruby%} class Order < ActiveRecord::Base def self.find_purchased # ... end def self.find_waiting_for_review # ... end def self.find_waiting_for_sign_off #..... end def self.find_waiting_for_sign_off #... end def self.advanced_search(fields, options = {}) #... end def self.simple_search(terms) #... end def to_xml #... end def to_json #... end def to_csv #... end def to_pdf #... end end {% endcodeblock %} Modules allow you to extract behavior into separate files.Modules also serve to group related information into labeled namespaces.Its improve readability of code {% codeblock lang:ruby%} class Order < ActiveRecord::Base extend OrderStateFinders extend OrderSearchers include OrderExporters end # lib/order_state_finders.rb module OrderStateFinders def find_purchased #... end def find_waiting_for_review #... end def find_waiting_for_sign_off #... end end # lib/order_searchers.rb module OrderSearchers def advanced_search(fields, options = {}) # ... end def simple_search(terms) # ... end end # lib/order_exporters.rb module OrderExporters def to_xml # ... end def to_json # ... end def to_csv # ... end def to_pdf # ... end end {% endcodeblock %} So in extend module's method are class method on that calling class.include module's methods are instance method for object of calling class

4.Use active record association Rails provides us association very nicely. {% codeblock lang:ruby%} class User < ActiveRecord::Base has_many :blogs end class blog < ActiveRecord::Base belongs_to :user end @user = User.find(params[:id]) @blogs = Blog.where(:user_id => params[:user_id]) {% endcodeblock %}

Instead of doing this.do

{% codeblock lang:ruby%} @user = User.find(params[:id]) @blogs = @user.blogs {% endcodeblock %}

5. Use Scope rather than writing complex finders {% codeblock lang:ruby%} class Book < ActiveRecord::Base def search_books(params={}) where('name like ? and price > ? and published_date > =?', "%#{params[:name]}%", 100,Date.today) end end {% endcodeblock %} Now suppose if you just need to find books based on published date you will create another method.That will duplicate your code {% codeblock lang:ruby%} class Book < ActiveRecord::Base def search_books(params={}) where('name like ? and price > ? and published_date > =?', "%#{params[:name]}%", 100,Date.today) end def search_by_published_date(date) where('published_date > =?',date) end end {% endcodeblock %} In this case you can use scope {% codeblock lang:ruby%} class Book < ActiveRecord::Base scope :by_published_date,lambda{|d|{:where => ['published_date >= ?',d]}} scope :by_name,lambda{|n|{:where => ['name like ?',"%#{n}%"]}} scope :by_price,lambda{|p|{:where => ['price =?',p}} end {% endcodeblock %} Now you can use scope like {% codeblock lang:ruby%} Book.by_published_date(Date.today).by_name('rails').by_price(100) {% endcodeblock %}

6. Do Metaprogramming {% codeblock lang:ruby%} class Plan < ActiveRecord::Base ACTIVE='active' INACTIVE = 'inactive' IN_PROGRESS = 'in progress' def active? status == ACTIVE end def inactive? status == INACTIVE end def in_progress? status == IN_PROGRESS end end {% endcodeblock %} now reduce code with meta programming {% codeblock lang:ruby%} class Plan < ActiveRecord::Base ACTIVE='active' INACTIVE = 'inactive' IN_PROGRESS = 'in progress' [ACTIVE, INACTIVE,IN_PROGRESS].each do |s| plan_status = <<-EOF def is_#{s}? self.status == '#{s}' end EOF class_eval plan_status, __FILE__, __LINE__ end end {% endcodeblock %}

7. Use full text search engine

if you app require search based on all the attribute on model or something like that then writing messy code is not an good idea. Better way is to use any search engine like Solr, Sphinx

Search engine indexed the data.so it gives you results based on search query against any full words in the indexed data

I have covered most of the steps here to enhance your Rails Models and keep your Rails Models clean, Here are some links to read more about these things. Reference links :

Thanks for reading this post :-)

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