代码学校截屏视频-从零开始使用Rails应用程序-第1部分错误：找不到带有“ id”的旅程=

Question

Following codeschool.com's ruby screencast on making an app and ran into this error.

Full error is

ActiveRecord::RecordNotFound in DestinationsController#show

Couldn't find Trip with 'id'=

The error applies to the @trip instance below

GET /destinations/1.json   
def show
@trip = Trip.find(params[:trip_id])

Here is the applicable code from the destinations_controller.rb:

 def show
    @trip = Trip.find(params[:trip_id])
    @destination = Destination.find(params[:id])
  end

Here is the Trip model

class Trip < ActiveRecord::Base
    has_many :destinations
end

And the Destination model

class Destination < ActiveRecord::Base

        belongs_to :trip
    end

Routes

Rails.application.routes.draw do
  resources :destinations

  resources :trips do 
    resources :destinations
  end

  root to: 'trips#index'

Any help is greatly appreciated. :) :) :)

Update 1 : From log files

Started GET "/destinations/4" for ::1 at 2016-03-31 00:50:08 +0900 Processing by DestinationsController#show as HTML Parameters: {"id"=>"4"}

[1m[35mDestination Load (0.6ms)[0m SELECT "destinations".* FROM "destinations" WHERE "destinations"."id" = ? LIMIT 1 [["id", 4]]

[1m[36mTrip Load (0.3ms)[0m [1mSELECT "trips".* FROM "trips" WHERE "trips"."id" = ? LIMIT 1[0m [["id", nil]]

Completed 404 Not Found in 20ms (ActiveRecord: 1.8ms)

ActiveRecord::RecordNotFound (Couldn't find Trip with 'id'=):
app/controllers/destinations_controller.rb:14:in `show'*

Update 2 : the destinations_controller in its entirety.

class DestinationsController < ApplicationController
  before_action :set_destination, only: [:show, :edit, :update, :destroy]

  # GET /destinations
  # GET /destinations.json
  def index
    @destinations = Destination.all
  end

  # GET /destinations/1
  # GET /destinations/1.json
  def show
    Rails.logger.debug params.inspect
    @trip = Trip.find(params[:trip_id])
    @destination = Destination.find(params[:id])
  end

  # GET /destinations/new
  def new
    @trip = Trip.find(params[:trip_id])
    @destination = Destination.new
  end

  # GET /destinations/1/edit
  def edit
    @trip = Trip.find(params[:trip_id])
    @destination = Destination.find(set_destination)
  end

  # POST /destinations
  # POST /destinations.json
  def create
    @trip = Trip.find(params[:trip_id])
    @destination = @trip.destinations.new(destination_params)

    respond_to do |format|
      if @destination.save
        format.html { redirect_to trip_destination_path(@trip, @destination), notice: 'Destination was successfully created.' }
        format.json { render :show, status: :created, location: @destination }
      else
        format.html { render :new }
        format.json { render json: @destination.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /destinations/1
  # PATCH/PUT /destinations/1.json
  def update
    respond_to do |format|
      if @destination.update(destination_params)
        format.html { redirect_to @destination, notice: 'Destination was successfully updated.' }
        format.json { render :show, status: :ok, location: @destination }
      else
        format.html { render :edit }
        format.json { render json: @destination.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /destinations/1
  # DELETE /destinations/1.json
  def destroy
    @destination.destroy
    respond_to do |format|
      format.html { redirect_to destinations_url, notice: 'Destination was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_destination
      @destination = Destination.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def destination_params
      params.require(:destination).permit(:name, :description)
    end
end

Answer 1

In your routes you currently have a nested route for destinations:

resources :trips do 
  resources :destinations
end

This means a destination is expected to be accessed in the context of its trip.

eg GET /trips/1/destinations/1.json where you'll have a trip_id parameter for the trip and an id parameter for the id of the destination.

You're also defining an non-nested route for destinations:

resources :destinations

but your DestinationController's show action assumes the nested version is being used when it does:

@trip = Trip.find(params[:trip_id])
@destination = Destination.find(params[:id])

Have a check that the GET request matches what's being shown in the screencast - or post a link to the exact screencast you're following.

Answer 2

Change the show action to this:

def show
  @trip = @destination.trip
end

Edit: Removed @destination assignment here because of the before_action running set_destination.

The Destination model has one Trip :

class Destination < ActiveRecord::Base
  belongs_to :trip
end

Since you're setting the @destination because id is actually passed over, you can just get @trip through association.