Create rails record from two ids - ruby-on-rails

Question

The functionality I'm trying to build allows Users to Visit a Restaurant.
I have Users, Locations, and Restaurants models.
Locations have many Restaurants.
I've created a Visits model with user_id and restaurant_id attributes, and a visits_controller with create and destroy methods.
Thing is, I can't create an actual Visit record. Any thoughts on how I can accomplish this? Or am I going about it the wrong way.
Routing Error
No route matches {:controller=>"restaurants", :location_id=>nil}
Code:
Routes:
location_restaurant_visits POST /locations/:location_id/restaurants/:restaurant_id/visits(.:format) visits#create
location_restaurant_visit DELETE /locations/:location_id/restaurants/:restaurant_id/visits/:id(.:format) visits#destroy
Model:
class Visit < ActiveRecord::Base
attr_accessible :restaurant_id, :user_id
belongs_to :user
belongs_to :restaurant
end
View:
<% #restaurants.each do |restaurant| %>
<%= link_to 'Visit', location_restaurant_visits_path(current_user.id, restaurant.id), method: :create %>
<% #visit = Visit.find_by_user_id_and_restaurant_id(current_user.id, restaurant.id) %>
<%= #visit != nil ? "true" : "false" %>
<% end %>
Controller:
class VisitsController < ApplicationController
before_filter :find_restaurant
before_filter :find_user
def create
#visit = Visit.create(params[:user_id => #user.id, :restaurant_id => #restaurant.id])
respond_to do |format|
if #visit.save
format.html { redirect_to location_restaurants_path(#location), notice: 'Visit created.' }
format.json { render json: #visit, status: :created, location: #visit }
else
format.html { render action: "new" }
format.json { render json: #visit.errors, status: :unprocessable_entity }
end
end
end
def destroy
#visit = Visit.find(params[:user_id => #user.id, :restaurant_id => #restaurant.id])
#restaurant.destroy
respond_to do |format|
format.html { redirect_to location_restaurants_path(#restaurant.location_id), notice: 'Unvisited.' }
format.json { head :no_content }
end
end
private
def find_restaurant
#restaurant = Restaurant.find(params[:restaurant_id])
end
def find_user
#user = current_user
end
end

Answer 1

I see a lot of problems here. The first is this line of code in your VisitController's create action (and identical line in your destroy action):
#visit = Visit.create(params[:user_id => #user.id, :restaurant_id => #restaurant.id])
params is a hash, so you should be passing it a key (if anything), not a bunch of key => value bindings. What you probably meant was:
#visit = Visit.create(:user_id => #user.id, :restaurant_id => #restaurant.id)
Note that you initialize #user and #restaurant in before filter methods, so you don't need to access params here.
This line of code is still a bit strange, though, because you are creating a record and then a few lines later you are saving it (if #visit.save). This is redundant: Visit.create initiates and saves the record, so saving it afterwards is pretty much meaningless. What you probably want to do is first initiate a new Visit with Visit.new, then save that:
def create
#visit = Visit.new(:user_id => #user.id, :restaurant_id => #restaurant.id)
respond_to do |format|
if #visit.save
...
The next thing I notice is that you have not initiated a #location in your create action, but you then reference it here:
format.html { redirect_to location_restaurants_path(#location), notice: 'Visit created.' }
Since you will need the location for every restaurant route (since restaurant is a nested resource), you might as well create a method and before_filter for it, like you have with find_restaurant:
before_filter :find_location
...
def find_location
#location = Location.find(params[:location_id])
end
The next problem is that in your view your location_restaurant_path is passed the id of current_user and of restaurant. There are two problems here. First of all the first argument should be a location, not a user (matching the order in location_restaurant_path). The next problem is that for the _path methods, you have to pass the actual object, not the object's id. Finally, you have method: :create, but the method here is referring to the HTTP method, so what you want is method: :post:
link_to 'Visit', location_restaurant_visits_path(#location, restaurant.id), method: :post
You'll have to add a find_location before filter to your RestaurantController to make #location available in the view here.
There may be other problems, but these are some things to start with.

Answer 2

location_id is nil and the path definition doesn't say (/:location_id) forcing a non-nil value there in order to route to that path; create a new route without location_id if you can derive it from a child's attribute (i.e. a restaurant_id refers to a Restaurant which already knows its own location_id).