Undefined method when saving an instance of my "Stop" model - ruby-on-rails

Question

My Rails App consists of touristic Routes. Each route has many stops and waypoints and stops have categories.
Waypoints are just the intermediate model between routes and stops because stops can belong to many routes.
So, when i try to save a Stop, i get the error:
undefined method `category' for #<Stop:0x007fa067acea90>
And the " if #stop.save" line is highlighted in red:
respond_to do |format|
if #stop.save
Waypoint.create(route_id: params[:route_id] , stop_id: #stop.id)
#print out category id or name here
category = params[:category]
In my stops controller i have this on create:
def create
#stop = Stop.new(stop_params)
respond_to do |format|
if #stop.save
Waypoint.create(route_id: params[:route_id] , stop_id: #stop.id)
#print out category id or name here
category = params[:category]
#once printed save it (stop category)
StopCategory.create(category_id: category, stop_id: #stop.id)
format.html { redirect_to #stop, notice: 'Stop was successfully created.' }
format.json { render :show, status: :created, location:#stop }
else
format.html { render :new }
format.json { render json: #stop.errors, status: :unprocessable_entity }
end
end
And on my waypoints controller i have this on create:
def create
#waypoint = Waypoint.create(waypoint_params)
redirect_to #waypoint.route
end
This is the stop model:
class Stop < ActiveRecord::Base
validates :description, length: { maximum: 140 }
validates :category, presence: true
#Image Uploader
mount_uploader :stop_image, StopImageUploader
#Relationship with stops and waypoints
has_many :waypoints
has_many :routes, through: :waypoints
# Relationship with categories
has_many :stop_categories
has_many :categories, through: :stop_categories
end
And this is the view where the form is :
<h2>Create a new stop:</h2><br>
<%= form_for(#stop) do |f| %>
<% if #stop.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#stop.errors.count, "error") %> prohibited this stop from being saved:</h2>
<ul>
<% #stop.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :name %><br>
<%= f.text_field :name %>
</div>
<select name="category" id=" " >
<option value="" disabled selected> Select a Category </option>
<% #categories.each do |category| %>
<option value="<%= category.id %>"> <%= category.name %> </option>
<% end %>
</select>
<div class="field">
<%= f.label :description %><br>
<%= f.text_area :description %>
</div>
<div class="field">
<%= f.label :stop_image %><br>
<%= f.file_field :stop_image %>
</div>
<div class="field">
<%= f.label :stop_lat %><br>
<%= f.number_field :stop_lat, :class => 'text_field', :step => 'any' %>
</div>
<div class="field">
<%= f.label :stop_long %><br>
<%= f.number_field :stop_long, :class => 'text_field', :step => 'any' %>
</div>
<%= hidden_field_tag :route_id, params[:id] %>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
<h2>Add existing stop</h2>
<br>
<%= form_for(#waypoint) do |f| %>
<div class="field">
<%= f.label :stop_id %><br>
<%= f.number_field :stop_id %>
</div>
<%= f.hidden_field :route_id %>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
<%= link_to 'Edit', edit_route_path(#route) %> |
<%= link_to 'Back', routes_path %>
<br>
<br>
<br>
</div>
Any ideas ?
Thanks!

Answer 1

Do you have a 'category' attribute in your Stop model? If not, then the following doesn't make sense:
validates :category, presence: true
That is where it's probably failing.
If you want to validate the presence of categories, you need to replace that check with something like this:
validate :has_categories
def has_categories # make this private
if categories.blank?
# add errors here
end
end
The following might also work:
validates :categories, presence: true

Answer 2

In the Stop model, you should replace the line
validates :category, presence: true
with
validates :categories, presence: true
because the validator takes the attribute/association name as argument, not the model name of the association.
Your association is called categories, so that's what you need to perform the validation on.