Form_forエラー：nilのための未定義メソッド `id '：NilClass

Question

私はワークアウトモデル、各ワークアウトhas_manyエクササイズ、そして各エクササイズhas_manyレポートを備えたアプリケーションを構築しています。次のように

私のルートは以下のとおりです。

 workouts GET /workouts(.:format)     workouts#index 
       POST /workouts(.:format)     workouts#create 
    new_workout GET /workouts/new(.:format)    workouts#new 
    edit_workout GET /workouts/:id/edit(.:format)   workouts#edit 
     workout GET /workouts/:id(.:format)    workouts#show 
       PATCH /workouts/:id(.:format)    workouts#update 
       PUT /workouts/:id(.:format)    workouts#update 
       DELETE /workouts/:id(.:format)    workouts#destroy 
     exercises GET /exercises(.:format)     exercises#index 
       POST /exercises(.:format)     exercises#create 
    new_exercise GET /exercises/new(.:format)    exercises#new 
    edit_exercise GET /exercises/:id/edit(.:format)   exercises#edit 
     exercise GET /exercises/:id(.:format)    exercises#show 
       PATCH /exercises/:id(.:format)    exercises#update 
       PUT /exercises/:id(.:format)    exercises#update 
       DELETE /exercises/:id(.:format)    exercises#destroy 
     reports POST /reports(.:format)      reports#create 
      report DELETE /reports/:id(.:format)     reports#destroy 

私はルートを入れ子におもちゃが、それは解決よりも、それは多くの問題を引き起こしたので、彼らは次のように残っている：私のworkouts#showページで

resources :workouts 
    resources :exercises 
    resources :reports, only: [:create, :destroy] 

そのワークアウトに練習問題を追加するリンクがあります：

<%= link_to 'Add/Edit Exercises', exercises_path(@workout) %> 

リンクをクリックすると、私は次のエラーを取得する：

undefined method `id' for nil:NilClass 

私はリンクをクリックすると、それは私のexercises#indexページに移動する必要があります

<h1>Current Exercises:</h1> 
    <% @exercises.each do |exercise| %> 
    <p><%= exercise.name %> (<%= link_to "Delete #{exercise.name}", exercise_path(exercise), method: :delete, data: { confirm: 'Are you sure?' } %>)</p> 
    <% end %> 
<h1>Add New Exercises:</h1> 
    <%= render 'exercises/form' %> 

それはエラーが示された行の上に、呼び出されていることをexercises/_form.html.erbであります：

<div class="row"> 
    <div class="col-xs-10 col-xs-push-1"> 
    <%= form_for @exercise, 
     :url => { :controller => "exercises", 
     :action => :create, 
     :workout_id => @workout.id } do |f| %> <!-- error called on this line --> 
     <div class="form-group"> 
     <%= f.label :name, class: 'sr-only' %> 
     <%= f.text_field :name, class: 'form-control', placeholder: "Enter exercise name" %> 
     </div> 

     <div class="form-group col-xs-4"> 
     <p><%= f.label :needs_seconds, class: 'sr-only' %> 
     <%= f.check_box :needs_seconds, class: 'check_box' %> Report seconds?</p> 
     </div> 

     <div class="form-group col-xs-4"> 
     <p><%= f.label :needs_reps, class: 'sr-only' %> 
     <%= f.check_box :needs_reps, class: 'check_box' %> Report reps?</p> 
     </div> 

     <div class="form-group col-xs-4"> 
     <p><%= f.label :needs_weight, class: 'sr-only' %> 
     <%= f.check_box :needs_weight, class: 'check_box' %> Report weight?</p> 
     </div> 

     <div class="text-center"><%= f.submit "Create Exercise", class: 'btn btn-primary' %></div> 

    <% end %> 
    </div> 
</div> 

このエラーの原因は何ですか？ここに私のトレーニングのコントローラです：

class WorkoutsController < ApplicationController 
    def index 
    @workouts = Workout.all 
    end 

    def show 
    @workout = Workout.friendly.find(params[:id]) 
    @exercise = Exercise.new 
    @report = Report.new 
    end 

    def new 
    @workout = Workout.new 
    @workout.user_id = current_user 
    end 

    def create 
    @workout = Workout.new(workout_params) 
    @workout.user = current_user 

    if @workout.save 
     flash[:notice] = "Workout was saved successfully." 
     redirect_to @workout 
    else 
     flash.now[:alert] = "Error creating workout. Please try again." 
     render :new 
    end 
    end 

    def edit 
    @workout = Workout.friendly.find(params[:id]) 
    @workout.user_id = current_user 
    end 

    def update 
    @workout = Workout.friendly.find(params[:id]) 

    @workout.name = params[:workout][:name] 
    @workout.workout_type = params[:workout][:workout_type] 
    @workout.teaser = params[:workout][:teaser] 
    @workout.description = params[:workout][:description] 
    @workout.video = params[:workout][:video] 
    @workout.difficulty = params[:workout][:difficulty] 
    @workout.trainer = params[:workout][:trainer] 
    @workout.user_id = params[:workout][:user_id] 

    if @workout.save 
     flash[:notice] = "Workout was updated successfully." 
     redirect_to @workout 
    else 
     flash.now[:alert] = "Error saving workout. Please try again." 
     render :edit 
    end 
    end 

    def destroy 
    @workout = Workout.friendly.find(params[:id]) 

    if @workout.destroy 
     flash[:notice] = "\"#{@workout.name}\" was deleted successfully." 
     redirect_to action: :index 
    else 
     flash.now[:alert] = "There was an error deleting the workout." 
     render :show 
    end 
    end 

    private 
    def workout_params 
    params.require(:workout).permit(:name, :workout_type, :teaser, :description, :video, :difficulty, :trainer, :user_id) 
    end 
end 

そしてここでは、演習コントローラです：

class ExercisesController < ApplicationController 
    before_action :authenticate_user! 


    def index 
    @exercises = Exercise.all 
    end 

    def new 
    @exercise = Exercise.new 
    end 

    def create 
    @workout = Workout.friendly.find(params[:workout_id]) 
    exercise = @workout.exercises.new(exercise_params) 
    exercise.user = current_user 

    if exercise.save 
     flash[:notice] = "Results saved successfully." 
     redirect_to [@workout] 
    else 
     flash[:alert] = "Results failed to save." 
     redirect_to [@workout] 
    end 
    end 

    def destroy 
    @workout = Workout.friendly.find(params[:workout_id]) 
    exercise = @workout.exercises.find(params[:id]) 

    if exercise.destroy 
     flash[:notice] = "Exercise was deleted successfully." 
     redirect_to [@workout] 
    else 
     flash[:alert] = "Exercise couldn't be deleted. Try again." 
     redirect_to [@workout] 
    end 
    end 

    private 

    def exercise_params 
    params.require(:exercise).permit(:name, :needs_seconds, :needs_weight, :needs_reps) 
    end 

    def authorize_user 
    exercise = Exercise.find(params[:id]) 
    unless current_user == current_user.admin? 
     flash[:alert] = "You do not have permission to create or delete an exercise." 
     redirect_to [exercise.workout] 
    end 
    end 
end 

そしてここでは、サーバログです：

Started GET "/exercises.abs-0002" for ::1 at 2016-06-01 13:10:33 -0700 
Processing by ExercisesController#index as 
    User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] 
    Workout Load (0.1ms) SELECT "workouts".* FROM "workouts" WHERE "workouts"."id" IS NULL LIMIT 1 
    Exercise Load (0.1ms) SELECT "exercises".* FROM "exercises" 
    Rendered exercises/_form.html.erb (9.6ms) 
    Rendered exercises/index.html.erb within layouts/application (18.4ms) 
Completed 500 Internal Server Error in 33ms (ActiveRecord: 0.3ms) 

NoMethodError - undefined method `id' for nil:NilClass: 
    app/views/exercises/_form.html.erb:4:in `block in _app_views_exercises__form_html_erb___1550785662008061170_70245396037240' 
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    actionview (4.2.5) lib/action_view/helpers/capture_helper.rb:38:in `capture' 
    actionview (4.2.5) lib/action_view/helpers/form_helper.rb:444:in `form_for' 
    app/views/exercises/_form.html.erb:3:in `_app_views_exercises__form_html_erb___1550785662008061170_70245396037240' 
    actionview (4.2.5) lib/action_view/template.rb:145:in `block in render' 
    activesupport (4.2.5) lib/active_support/notifications.rb:166:in `instrument' 
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    actionview (4.2.5) lib/action_view/template.rb:143:in `render' 
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    activesupport (4.2.5) lib/active_support/notifications.rb:164:in `instrument' 
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    actionview (4.2.5) lib/action_view/helpers/rendering_helper.rb:35:in `render' 
    app/views/exercises/index.html.erb:7:in `_app_views_exercises_index_html_erb___2271140629366515446_70245347113980' 
    actionview (4.2.5) lib/action_view/template.rb:145:in `block in render' 
    activesupport (4.2.5) lib/active_support/notifications.rb:166:in `instrument' 
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    actionview (4.2.5) lib/action_view/renderer/template_renderer.rb:54:in `block (2 levels) in render_template' 
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    /Users/elizabethbayardelle/.rbenv/versions/2.2.4/lib/ruby/2.2.0/benchmark.rb:303:in `realtime' 
    activesupport (4.2.5) lib/active_support/core_ext/benchmark.rb:12:in `ms' 
    actionpack (4.2.5) lib/action_controller/metal/instrumentation.rb:44:in `block in render' 
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    actionpack (4.2.5) lib/action_controller/metal/instrumentation.rb:43:in `render' 
    meta-tags (2.1.0) lib/meta_tags/controller_helper.rb:26:in `render_with_meta_tags' 
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    rack (1.6.4) lib/rack/handler/webrick.rb:88:in `service' 

Answer 1

あなたlink_toはworkouts#showで以下のようにすることができます：

<%= link_to 'Add/Edit Exercises', exercises_path(workout_id: @workout.id) %> 

あなたはは、次のようにexercises/_form.html.erbの隠しフィールドにをworkout_id渡すことができexercises_controller.rb

def index 
    @workout = Workout.find_by_id(params[:workout_id]) 
    @exercise = Exercise.new 
    @exercises = Exercise.all 
end 

：

<%= form_for @exercise do |f| %> 
    <%= f.hidden_field :workout_id, @workout.id %> 
<% end %> 

をそして、次のように強いのparamにworkout_idが含まれています

を

def exercise_params 
    params.require(:exercise).permit(:name, :needs_seconds, :needs_weight, :needs_reps, :workout_id) 
end