定義されていないメソッド `nil 'のための` following'：NilClass

Question

私はtwitterクローンに似たプロジェクトに取り組んでいます。しかし、私は次のようなエラーに遭遇しています：未定義のメソッド `following 'for nil：私のコントローラのNilClass。だから、開始するには、ここに私のコントローラである：

class User < ActiveRecord::Base 
# Include default devise modules. Others available are: 
# :confirmable, :lockable, :timeoutable and :omniauthable 
    devise :database_authenticatable, :registerable, 
    :recoverable, :rememberable, :trackable, :validatable 

    serialize :following, Array  
    has_many :tweets 

    validates :username, presence: true, uniqueness: true 
end 

マイスキーマ：

ActiveRecord::Schema.define(version: 20160811164903) do 

create_table "tweets", force: :cascade do |t| 
    t.string "message" 
    t.integer "user_id" 
    t.datetime "created_at", null: false 
    t.datetime "updated_at", null: false 
end 

create_table "users", force: :cascade do |t| 
    t.string "email",     default: "", null: false 
    t.string "encrypted_password",  default: "", null: false 
    t.string "reset_password_token" 
    t.datetime "reset_password_sent_at" 
    t.datetime "remember_created_at" 
    t.integer "sign_in_count",   default: 0, null: false 
    t.datetime "current_sign_in_at" 
    t.datetime "last_sign_in_at" 
    t.string "current_sign_in_ip" 
    t.string "last_sign_in_ip" 
    t.datetime "created_at",       null: false 
    t.datetime "updated_at",       null: false 
    t.string "name" 
    t.string "username" 
    t.text  "bio" 
    t.string "location" 
    t.text  "following" 
end 

add_index "users", ["email"], name: "index_users_on_email", unique: true 
add_index "users", ["reset_password_token"], name:  
"index_users_on_reset_password_token", unique: true 

end 

最後に自分のアプリケーションのコントローラ：

class EpicenterController < ApplicationController 

def feed 
#Here we initialize the array that will hold tweets from the current_user's  
    following list. 
@following_tweets = [] 

    Tweet.all.each do |tweet| 
    if current_user.following.include?(tweet.user_id) 
    @following_tweets.push(tweet) 
    end 
    end 
end 

def show_user 
    @user = User.find(params[:id]) 
end 

def now_following 
    @user = User.find(params[:follow_id]) 

    #Adding the user.id of the user you want to follow to your 'follow' array 
    attribute 
    current_user.following.push(params[:follow_id].to_i) 

    current_user.save 
end 

def unfollow 
end 

終わりここ

は私のモデルであり、

class ApplicationController < ActionController::Base 
    # Prevent CSRF attacks by raising an exception. 
    # For APIs, you may want to use :null_session instead. 
    protect_from_forgery with: :exception 

    before_action :configure_permitted_parameters, if: :devise_controller? 

    protected 

    def configure_permitted_parameters 

    devise_parameter_sanitizer.permit(:sign_up, keys: [:name, :username, 
    :bio,  
    :location, :following]) 

    devise_parameter_sanitizer.permit(:account_update, keys: [:name, 
    :username, :bio, :location, :following]) 
    end 
end 

ご協力いただきありがとうございます。あなたが何か他のものを見る必要がある場合は私に教えてください。私はそれを追加します。

スタックトレース：あなたはそれを処理する必要がありますので、

NoMethodError (undefined method `following' for nil:NilClass): 
app/controllers/epicenter_controller.rb:8:in `block in feed' 
app/controllers/epicenter_controller.rb:7:in `feed' 


Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/actionpack- 
4.2.6/lib/action_dispatch/middleware/templates/rescues/_source.erb (3.9ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/actionpack- 
4.2.6/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb  
(2.7ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/actionpack- 
4.2.6/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (0.9ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/actionpack- 
4.2.6/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb 
within rescues/layout (63.4ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/web-console- 
2.3.0/lib/web_console/templates/_markup.html.erb (0.4ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/web-console- 
2.3.0/lib/web_console/templates/_inner_console_markup.html.erb within 
layouts/inlined_string (0.3ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/web-console- 
2.3.0/lib/web_console/templates/_prompt_box_markup.html.erb within  
layouts/inlined_string (0.3ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/web-console- 
2.3.0/lib/web_console/templates/style.css.erb within layouts/inlined_string 
(0.5ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/web-console- 
2.3.0/lib/web_console/templates/console.js.erb within layouts/javascript 
(62.0ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/web-console- 
2.3.0/lib/web_console/templates/main.js.erb within layouts/javascript 
(0.3ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/web-console- 
2.3.0/lib/web_console/templates/error_page.js.erb within layouts/javascript 
(0.6ms) 
Rendered /Users/mikecuddy/.rvm/rubies/ruby- 
2.2.1/lib/ruby/gems/2.2.0/gems/web-console- 
2.3.0/lib/web_console/templates/index.html.erb (139.5ms) 

Answer 1

current_userは、ユーザーがログインしていないためnilです：

if user_signed_in? 
    current_user.following # ... 
else 
    store_location_for :user, request.path 
    redirect_to new_user_session_path, alert: 'You need to be logged in to do that.' 
end 

または

class EpicenterController < ApplicationController 
    before_action :authenticate_user! #, only: [:feed, :now_following] (optional) 
    # ... 
end 

あなたのコントローラの場合主にサインインされたユーザーを対象としています（そのように見えます）。