ruby on rails - has_many, new, and single table inheritance -

i have 3 models (student, document, , cv). document has single table inheritance. question how create cv off of @student? i've tried @student.documents.new(type: cv) gives me:

error

nomethoderror: undefined method `safe_constantize' #<class:0x007fd1819adad0> 

i know can cv.new(owner: @student) doesn't feel elegant.

models

class student < activerecord::base   has_many :documents,     as: :owner end  class document < activerecord::base   has_many :documents,     as: :owner end  class cv < document end 

your answer is:

@cv = @student.documents.build @cv.type = "cv" 

see activerecord::associations::collectionproxy#build