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rails_model.rb
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This guide applies to a Ruby on Rails ActiveRecord Model class. It is part of Jo Hund’s Software Engineering Guide.

This convention puts the most important information about a model at the top.

 

      		
    

    

      
        

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class Project < ActiveRecord::Base
  

      		
    

    

      
        

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 Include other modules: They add new behavior to the model. We want to know about
 this right away.

      		
      
        
  include Canable::Permissions
  

      		
    

    

      
        

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 Rails macros: They, too add implicit behavior to our model.

      		
      
        
  acts_as_list
  default_scope order("name ASC")
    

      		
    

    

      
        

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 ActiveRecord callbacks: They add important behavior to our model.



 It’s also important to specify callbacks before associations in order for inheritance to work
 for the callback queues. Otherwise, you might trigger the loading of a child before the parent
 has registered the callbacks and they won’t be inherited. (From Rails' ActiveRecord::Callbacks
 documentation)



    

  • Sort the callbacks as required by model logic and add a comment indicating why a callback’s
position is important.
    • 


      		
      
        
  before_create :set_start_date # no dependencies, do this first
  before_save :update_duration # after set_start_date so we can use start date for calculation
  

      		
    

    

      
        

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 ActiveRecord associations: They tell us how this model interacts with other models.



    

  • Sort the associations alphabetically, including the macro. Helps with detecting duplicates and
finding them.
    • 

  • Never go over 100 characters per line.
    • 

  • Prefer has_many :through over has_and_belongs_to_many
    • 

  • Always spell out the :dependent option explicitly where it applies to prove that you have
thought about it.
    • 

  • Always specify the :inverse_of option on associations.
Helps eliminating some strange bugs when traversing the object graph in-memory and making changes.
Except on :as, :through and :polymorphic associations. Doesn’t work on those.
    • 


      		
      
        
  belongs_to :client, :inverse_of => :projects
  has_many :collaborators, :dependent => :nullify, :inverse_of => :project
  has_many :todos, :order => "position ASC", :dependent => :destroy, :inverse_of => :project
  has_many :persons_responsible,
    :through => :collaborators,
    :uniq => true,
    :source => :person,
    :order => "persons.email ASC"

      		
    

    

      
        

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 Validations

      		
      
        
  validates_presence_of :name
  

      		
    

    

      
        

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 Scopes (formerly known as named_scopes)



    

  • Sort scopes alphabetically
    • 

  • Never go over 100 characters per line.
    • 

  • For complex scopes, put each element on a new line, put . on previous line to make
multi-line unambiguous for parser
    • 


      		
      
        
  scope :active, where(:state => "active")
  scope :sorted_by lambda { |sort_key|
    case sort_key
    when "date_asc"; "projects.created_at ASC"
    ...
    end
  }
  scope :complicated,
    where("other_table.some_value = ?", value).
    order("position ASC").
    joins("other_table").
    limit(10)
    

      		
    

    

      
        

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 Miscellaneous Declarations:



    

  • state_machine
    • 

  • delegation
    • 


      		
      
        
  attr_protected :client_id
  alias_method ...

      		
    

    

      
        

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 I prefer the demeter ruby extension over Rails' delegate for delegation.

      		
      
        
  demeter :client_name, :to => :client, :using => :name
  

      		
    

    

      
        

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 Class Methods



 I prefer the def self.method_name form. Shows the class context when looking at the method in isolation
 (e.g. as part of search results or symbol search in editor)

      		
      
        
  def self.class_method_1
  end
  
  def self.class_method_2
  end
  

      		
    

    

      
        

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 Instance Methods

      		
      
        
  def instance_method_1(arg1)
  end
  
  def instance_method_2(arg1)
  end
  

      		
    

    

      
        

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 Permissions



 Permissions are all grouped together (both class and instance methods)

      		
      
        
  def self.listable_by?(actor)
    actor.is_admin?
  end
  
  def updatable_by?(actor)
    owned_by?(actor)
  end
  
  def owned_by?(actor)
    actor == person
  end
  

      		
    

    

      
        

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 Protected Methods: The protected keyword is not indented.

      		
      
        
protected

  def protected_method
  end
  

      		
    

    

      
        

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 Private Methods: The private keyword is not indented.

      		
      
        
private

  def set_start_date
    self.started_at = Time.zone.now
  end

end

      		
    

    

      
        

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 This document was generated with rocco.rb



 © Jo Hund