ruby on rails - You cannot call create unless the parent is saved -

i have iteration

      current_item = line_items.create(product_id: product_id, instruction: instruction)       current_item.save       attribute_values.each |attribute|         current_item.line_item_attributes.create(product_attribute_id: attribute)       end 

and gives me error on creating attributes. when print out current_item

#<lineitem id: nil, product_id: 1, cart_id: 36, created_at: nil, updated_at: nil, quantity: 1, instruction: "", order_id: nil> 

which understanding means it's not saved yet. how can fix this?

after calling create! error returned is:

validation failed: order must exist 

the order model added migration:

class addordertolineitem < activerecord::migration[5.0]   def change     add_reference :line_items, :order, index: true, foreign_key: true   end end 

and lineitem belongs_to :order. issue here want blank, because in case doesn't belong order yet.