Agile Web Development with Rails, Edition 5

10.3 Iteration E3: Finishing the Cart 10.1 Iteration E1: Creating a Smarter Cart

10.2 Iteration E2: Handling Errors

Log errors and show them on the screen.

Rescue error: log, flash, and redirect.

edit app/controllers/carts_controller.rb
class CartsController < ApplicationController
  before_action :set_cart, only: [:show, :edit, :update, :destroy]
  rescue_from ActiveRecord::RecordNotFound, with: :invalid_cart
  # GET /carts
  # ...
  private
  # ...
 
    def invalid_cart
      logger.error "Attempt to access invalid cart #{params[:id]}"
      redirect_to store_index_url, notice: 'Invalid cart'
    end
end

Reproduce the error.

get /carts/wibble
You are being redirected.
get http://localhost:3000/

Invalid cart

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Inspect the log.

tail -25 log/development.log
  Rendering /home/rubys/git/rails/actionpack/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout
  Rendering /home/rubys/git/rails/actionpack/lib/action_dispatch/middleware/templates/rescues/_source.html.erb
  Rendered /home/rubys/git/rails/actionpack/lib/action_dispatch/middleware/templates/rescues/_source.html.erb (1.8ms)
  Rendering /home/rubys/git/rails/actionpack/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb
  Rendered /home/rubys/git/rails/actionpack/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (0.9ms)
  Rendering /home/rubys/git/rails/actionpack/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb
  Rendered /home/rubys/git/rails/actionpack/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (0.6ms)
  Rendered /home/rubys/git/rails/actionpack/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout (12.1ms)
Started GET "/carts/wibble" for 127.0.0.1 at 2017-03-26 03:41:39 -0400
Processing by CartsController#show as HTML
  Parameters: {"id"=>"wibble"}
  Cart Load (0.1ms)  SELECT  "carts".* FROM "carts" WHERE "carts"."id" = ? LIMIT ?  [["id", 0], ["LIMIT", 1]]
Attempt to access invalid cart wibble
Redirected to http://localhost:3000/
Completed 302 Found in 4ms (ActiveRecord: 0.6ms)
 
 
Started GET "/" for 127.0.0.1 at 2017-03-26 03:41:39 -0400
Processing by StoreController#index as HTML
  Rendering store/index.html.erb within layouts/application
  Product Load (0.2ms)  SELECT "products".* FROM "products" ORDER BY "products"."title" ASC
  Rendered store/index.html.erb within layouts/application (9.3ms)
Completed 200 OK in 31ms (Views: 27.5ms | ActiveRecord: 0.5ms)
 
 

Limit access to product_id

edit app/controllers/line_items_controller.rb
    # Never trust parameters from the scary internet, only allow the white
    # list through.
    def line_item_params
      params.require(:line_item).permit(:product_id)
    end
rails test:controllers
Run options: --seed 61840
 
# Running:
 
.......................
 
Finished in 0.636743s, 36.1213 runs/s, 54.9673 assertions/s.
 
23 runs, 35 assertions, 0 failures, 0 errors, 0 skips

Inspect the log.

grep -B 8 -A 7 "Unpermitted parameter" log/test.log
-----------------------------------------------------
LineItemsControllerTest: test_should_update_line_item
-----------------------------------------------------
  LineItem Load (0.1ms)  SELECT  "line_items".* FROM "line_items" WHERE "line_items"."id" = ? LIMIT ?  [["id", 980190962], ["LIMIT", 1]]
Started PATCH "/line_items/980190962" for 127.0.0.1 at 2017-03-26 03:41:41 -0400
Processing by LineItemsController#update as HTML
  Parameters: {"line_item"=>{"cart_id"=>"980190962", "product_id"=>"298486374"}, "id"=>"980190962"}
  LineItem Load (0.0ms)  SELECT  "line_items".* FROM "line_items" WHERE "line_items"."id" = ? LIMIT ?  [["id", 980190962], ["LIMIT", 1]]
Unpermitted parameter: cart_id
   (0.0ms)  SAVEPOINT active_record_1
  Product Load (0.0ms)  SELECT  "products".* FROM "products" WHERE "products"."id" = ? LIMIT ?  [["id", 298486374], ["LIMIT", 1]]
  Cart Load (0.0ms)  SELECT  "carts".* FROM "carts" WHERE "carts"."id" = ? LIMIT ?  [["id", 980190962], ["LIMIT", 1]]
   (0.0ms)  RELEASE SAVEPOINT active_record_1
Redirected to http://www.example.com/line_items/980190962
Completed 302 Found in 4ms (ActiveRecord: 0.2ms)
   (0.0ms)  rollback transaction
edit test/controllers/line_items_controller_test.rb
  test "should update line_item" do
    patch line_item_url(@line_item),
      params: { line_item: { product_id: @line_item.product_id } }
    assert_redirected_to line_item_url(@line_item)
  end
rake log:clear LOGS=test
rails test:controllers
Run options: --seed 38825
 
# Running:
 
.......................
 
Finished in 0.716801s, 32.0870 runs/s, 48.8281 assertions/s.
 
23 runs, 35 assertions, 0 failures, 0 errors, 0 skips
grep "Unpermitted parameters" log/test.log | wc -l
0

10.3 Iteration E3: Finishing the Cart 10.1 Iteration E1: Creating a Smarter Cart