Rails Nested Forms Not Updating Nested Model - ruby-on-rails

Question

I am having trouble trying to update nested models in my form. I don't get any errors and but the attributes don't get updated.
I have the following model:
class Trip < ActiveRecord::Base
has_many :segments
accepts_nested_attributes_for :segments, allow_destroy: true
end
class Segment < ActiveRecord::Base
belongs_to :start_location, class_name: 'Location'
belongs_to :end_location, class_name: 'Location'
belongs_to :trip
validates_presence_of :date, :start_location, :end_location
end
class Location < ActiveRecord::Base
has_many :segments
end
And have this code in the _form.html.erb:
<%= form_for #trip do |f| %>
...
<%= f.fields_for :segments do |builder| %>
<%= render 'segment_fields', f: builder %>
<% end %>
...
<% end %>
And this in the partial _segment_fields.html.erb:
<%= f.collection_select :start_location_id, Location.order(:name), :id, :name %> -
<%= f.collection_select :end_location_id, Location.order(:name), :id, :name %> <br>
<%= f.date_field :date %>
In my controller I also permited the assigment of :segments_attributes
def trip_params
params.require(:trip).permit(:name, :start_date, :end_date, :segments_attributes)
end
Does anybody know what I am lacking or doing wrong?

Answer 1

When you are creating a new record you don't need its id to be permitted as it's not been created but when you want to update your record you need to pass id to the permitted attributes, else it will work with create but not when you want to update your record, so you need to do:
def trip_params
params.require(:trip).permit(:id, :name, :start_date, :end_date, segments_attributes: [:id,:start_location_id,:end_location_id, :date])
end