ruby on rails - Helper method called upon in model file, not working -

in create method in controller have:

if logged_in_admin?   @invitation.set_ids 

in invitation model:

def set_ids   self.person_one_id = current_user.id end 

current_user method in app/helpers/sessions_helper.rb , defines logged in user. use method in many controller methods. however, use case above error message undefined local variable or method 'current_user' #<invitation:0x007f699086bf40>.

why error message? because time i'm using helper method in model file , not allowed? if such not allowed, best way securely set person_one_id @invitation equal id of logged in user?

current_user not available in model layer(it's mvc, helpers on cv layer , model know nothing current_user helper). pass user_id helper argument:

some_helper.rb

def my_helper   if logged_in_admin?     @invitation.set_ids(current_user.id) # ..... 

model.rb:

def set_ids(user_id)   self.person_one_id = user_id end