Get Relationship typ of an association

Question

I create dynamic classes for my models using rails/mongoid. I want to automatically include certain associated records (belongs_to, has_one) whenever I access a record. Therefore I need to include all these association in my as_json function.

The method 'associations' gives me all associated models - but I need to filter only the type of associations I want to include (if I include the has_many association I will get a huge time consuming database request and I dont need these data). How can I filter the output of the the association method to get only the required associations?

I tried to loop through all associations:

  def as_json(options={})
    selected_associations=[]
    associations.each do |ass|
      puts "Association:: ", ass, ass=>relation
      if association=='Belongs_To'       # Need the right instruction here
         selected_associations.push(ass) 
      end 
    end
    attrs = super(:include => selected_associations)

  end

Puts delivers me for each association following output on the console (entity is one model):

Association: entities {:relation=>Mongoid::Relations::Referenced::Many, :extend=>nil, :inverse_class_name=>"WSAEntity", :name=>"entities", :class_name=>"WSAEntity", :validate=>true}

How can I assess the ':relation=>...' attribute so I can use this to select the types of associations I need and correct my code above? Or there is an even better way to get an array with all my filtered associations?

Thanks, Michael

Jagdeep Singh Jagdeep Singh · Accepted Answer · 2017-12-27T12:02:08

Try this:

associations.each do |key, value|
  ...
  if value.macro == :belongs_to        # OR you can do `value.relation == Mongoid::Relations::Referenced::In`
    selected_associations.push(key)    # OR `value`, you need to decide what you need here
  end 
end

key is the name of association here e.g. "user".

value looks something like this:

#<Mongoid::Relations::Metadata
autobuild:    false
class_name:   User
cyclic:       nil
counter_cache:false
dependent:    nil
inverse_of:   nil
key:          user_id
macro:        belongs_to
name:         user
order:        nil
polymorphic:  false
relation:     Mongoid::Relations::Referenced::In
setter:       user=
versioned:    false>

Get Relationship typ of an association

1 Answers