rails ams, Nested models undefined method `' for nil:NilClass - ruby-on-rails

Question

I have the following models:
class Appeal < ActiveRecord::Base
belongs_to :applicant, :autosave => true
belongs_to :appealer, :autosave => true
end
class Appealer < ActiveRecord::Base
has_many :appeals, :autosave => true
end
class Applicant < ActiveRecord::Base
has_many :appeals
end
What I want is for every appealer to hold a reference to the applicant of his last appeal
so I modified Appealer model to:
class Appealer < ActiveRecord::Base
has_many :appeals, :autosave => true
def last_applicant
return self.appeals.last.applicant
end
end
but I get the error:
undefined method `applicant' for nil:NilClass
what is strange that if I debug this (via RubyMine - Evaluate Expression) I can get the applicant.
If I try to get the last appeal:
class Appealer < ActiveRecord::Base
has_many :appeals, :autosave => true
def last_appeal
return self.appeals.last
end
end
everything works.
Im working with active-model-serializer, tried to do it also in the serializer (I actually need this value on a specific call - not allover the model) but it also didnt worked with the same errors.
the AMS code:
class AppealerTableSerializer < ActiveModel::Serializer
attributes :id, :appealer_id, :first_name, :last_name, :city
has_many :appeals, serializer: AppealMiniSerializer
def city
object.appeals.last.appealer.city
end
end
MY QUESTION:
How can I get the nested object attributes in my JSON?
What am I doing wrong?
EDIT:
My controller call:
class AppealersController < ApplicationController
def index
appealers = Appealer.all
render json: appealers, each_serializer: AppealerTableSerializer, include: 'appeal,applicant'
end
end
I've tried with and without the include, still not works

Answer 1

Maybe I am missing something, because this looks like you have Appealer record that doesn't have any appeals yet.
In such case, this code
def last_appeal
return self.appeals.last
end
Will return nil, which won't raise any errors. But if you call this
def last_applicant
return self.appeals.last.applicant
end
return self.appeals.last is nil and you try to call applicant method on nil object instead of Appeal object.
To fix it just add check for nil
class Appealer < ActiveRecord::Base
has_many :appeals, :autosave => true
def last_applicant
last = self.appeals.last
if last.nil?
return nil
else
return last.applicant
end
end
end