query optimization - Preventing N+1 queries in Rails -

I have seen some examples of a passing: hash value to any one in ActiveRecord Railway < Code> find methods However, I have not seen any examples that it is possible through methods of relationship or not. For example, suppose I have the following:

  def user & lt; ActiveRecord :: Base has has_many: user_favorites has_many: favorites, via = & gt; : User_favorites end def favorites & lt; ActiveRecord :: Base has has_many: user_favorites has_many: users ,: through = & gt; : User_favorites end def UserFavorite & lt; ActiveRecord :: Base is_to: user is_to: Favorites end   
 All examples I see in this way:  
  User.find (: all :, < = Code> Preferred   
 But I do not see any examples of the use of relationships, would it be possible to do something like this instead?  
  User: (Relationships = & gt ;: User)    
 
 
 You class relationships Can not be used as management. This is the example methods.  
 
 
 
  
  
  
  
  
 < Code> User.find (: all ,: include = & gt;: preferred)   
 or for Rail 3.x  
> Code> User.includes (: Favorites)