常連

注目の的

自己紹介

###前提・実現したいこと
rails4 ローカル環境

現在メッセージ機能を実装してラインのようなメッセージのやりとりができるようにしたいと思っています。   

機能自体は実装できたのですが、会話一覧ページ（誰とメッセージのやり取りをしているか表示するラインのトーク一覧のようなページ）で、メッセージのやり取りをしている各ユーザーとの最新のメッセージを一件だけ取得する方法が分かりません。

conversations : 会話情報を格納するテーブル
messages : 会話の個々のメッセージを格納するテーブル
として実装しました。 

###発生している問題・エラーメッセージ

``#<Message:0x007fdab6718200>``
と表示されてしまい、メッセージの内容（body）を取得できません。

###該当のソースコード
``conversations/index.html.erb``ここで最新のメッセージを一件だけ取得したい
```
<div class="container message">
  <div class="wrapper col-md-8 col-md-offset-2 col-sm-10 message-index">
      <h2>メッセージ一覧</h2>

      <% @conversations.each do |conversation| %>
      <div class="row conversation-list">
        <% if conversation.target_user(current_user).present? %>
          <%= link_to conversation.target_user(current_user).name, conversation_messages_path(conversation)%>
        <% end %>
      </div>
      <%= conversation.messages.order(created_at: :desc).take %>
      <% end %>
  </div>
</div>
```

どのように修正したら良いのでしょうか？
必要であればコントローラーやモデルなども記載しますので、アドバイス頂けると助かります。
よろしくお願いします。

Ruby on Rails　会話一覧で最新のメッセージを一件だけ表示させたい

### 前提・実現したいこと

現場で使えるRubyonRails5速習実践ガイドをDocker環境で学習しています。
Rspecでの検証において、`visit task_path(task_a)`でエラーが出ました。


```
NameError:undefined local variable or method 'task_a' for #<RSpec::ExampleGroups::Nested::Nested_2::A:0x000055f5b4270a60>
```

調べてみると、spec_helper.rbに以下を追加すると解決するそうなのですが、次は`Rails.application.routes.url_helpers`が読み込めないというエラーが発生してしまいます。

```
RSpec.configure do |config|
  config.include Rails.application.routes.url_helpers
end
```

参考
[stackoverflow「Rspec and named routes」](https://stackoverflow.com/questions/22741975/undefined-local-variable-or-method-root-path)

エラーメッセージ
```
An error occurred while loading spec_helper.
Failure/Error: config.include Rails.application.routes.url_helpers

NameError:
  uninitialized constant Rails
# ./spec/spec_helper.rb:19:in `block in <top (required)>'
# ./spec/spec_helper.rb:18:in `<top (required)>'

An error occurred while loading ./spec/system/tasks_spec.rb.
Failure/Error: config.include Rails.application.routes.url_helpers

NameError:
  uninitialized constant Rails
# ./spec/spec_helper.rb:19:in `block in <top (required)>'
# ./spec/spec_helper.rb:18:in `<top (required)>'
# ./spec/rails_helper.rb:2:in `require'
# ./spec/rails_helper.rb:2:in `<top (required)>'
# ./spec/system/tasks_spec.rb:1:in `require'
# ./spec/system/tasks_spec.rb:1:in `<top (required)>'
No examples found.
```

### 該当のソースコード

spec/system/tasks_spec.rb
```
require 'rails_helper'

describe 'タスク管理機能',type: :system do
  describe '一覧表示機能' do
    let(:user_a){ FactoryBot.create(:user, name: 'ユーザーA', email: 'a@example.com') }
    let(:user_b){ FactoryBot.create(:user, name: 'ユーザーB', email: 'b@example.com') }
    let!(:task_a){ FactoryBot.create(:task, name: '最初のタスク', user: user_a) }

    before do
      FactoryBot.create(:task, name: '最初のタスク', user: user_a)
      visit login_path
      fill_in 'メールアドレス', with: login_user.email
      fill_in 'パスワード', with: login_user.password
      click_button 'ログインする'
    end

    context 'ユーザーAがログインしているとき' do
      let(:login_user) { user_a }

      it 'ユーザーAが作成したタスクが表示される' do
        expect(page).to have_content '最初のタスク'
      end
    end

    context 'ユーザーBがログインしているとき' do
      let(:login_user) { user_b }

      it 'ユーザーAが作成したタスクが表示されない' do
        # ユーザーAが作成したタスクが画面上に表示されないことを確認
        expect(page).not_to have_content '最初のタスク'
      end
    end
  end

  describe '詳細表示機能' do
    context 'ユーザーAがログインしているとき' do
      let(:login_user) { user_a }

      before do
        visit task_path(task_a)
      end

      it 'ユーザーAが作成したタスクが表示される' do
        expect(page).to have_content '最初のタスク'
      end
    end
  end
end

```

spec/spec_helper.rb
```ruby
require 'capybara/rspec'

RSpec.configure do |config|
  config.include Rails.application.routes.url_helpers
  config.before(:each, type: :system) do
    driven_by :selenium_chrome_headless
  end

  config.expect_with :rspec do |expectations|
    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
  end

  config.mock_with :rspec do |mocks|
    mocks.verify_partial_doubles = true
  end

  config.shared_context_metadata_behavior = :apply_to_host_groups

end

```

spec/rails_helper.rb
```
require 'spec_helper'
ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
abort("The Rails environment is running in production mode!") if Rails.env.production?
require 'rspec/rails'

begin
  ActiveRecord::Migration.maintain_test_schema!
rescue ActiveRecord::PendingMigrationError => e
  puts e.to_s.strip
  exit 1
end

RSpec.configure do |config|
  config.fixture_path = "#{::Rails.root}/spec/fixtures"
  config.use_transactional_fixtures = true
  config.infer_spec_type_from_file_location!
  config.filter_rails_from_backtrace!
end
```

Gemfile
```
source 'https://rubygems.org'


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.1.4'
# Use postgresql as the database for Active Record
gem 'pg', '~> 0.18'
# Use Puma as the app server
gem 'puma', '~> 3.7'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 3.0'
# Use ActiveModel has_secure_password
gem 'bcrypt', '~> 3.1.7'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
  gem 'factory_bot_rails', '~> 4.11'
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '~> 2.13'
  gem 'selenium-webdriver'
  gem 'webdrivers', '~> 3.0'
  gem 'rspec-rails', '~> 3.7'
  gem 'rails-controller-testing'
end

group :development do
  # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
  gem 'web-console', '>= 3.3.0'
  gem 'listen', '>= 3.0.5', '< 3.2'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

# for slim
gem 'slim-rails'
gem 'html2slim'

gem 'bootstrap'

gem 'rails_autolink'

```


### 補足情報（FW/ツールのバージョンなど）

* Docker version 18.09.2
* docker-compose version 1.23.2
* ruby 2.5.5
* Rails 5.2.3

『Ruby on Rails 5 速習実践ガイド』のRSpecで「visit 〇〇_path」が使用できない

###前提・試したいこと
Railsを学習し始めてから3ヶ月ほどの初心者です。

RSpecにて、FactoryBotを用いて、ユーザーの作成をしたいのですが、NameErrorになります。

###発生している問題・エラーメッセージ
```
Failure/Error: config.include FactoryBot::Syntax::Methods

NameError:
  uninitialized constant FactoryBot
# /usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/active_support.rb:79:in `block in load_missing_constant'
# /usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/active_support.rb:8:in `without_bootsnap_cache'
# /usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/active_support.rb:79:in `rescue in load_missing_constant'
# /usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/active_support.rb:58:in `load_missing_constant'
# ./spec/rails_helper.rb:63:in `block in <top (required)>'
# ./spec/rails_helper.rb:35:in `<top (required)>'
# ./spec/requests/worker_users_spec.rb:1:in `<top (required)>'
# ------------------
# --- Caused by: ---
# NameError:
#   uninitialized constant FactoryBot
#   /usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/active_support.rb:60:in `block in load_missing_constant'
No examples found.


Finished in 0.00012 seconds (files took 7.56 seconds to load)
0 examples, 0 failures, 1 error occurred outside of examples
```

###該当のソースコード
requests/worker_user_spec.rb
```
require 'rails_helper'

RSpec.describe "WorkerUsers", type: :request do
  describe "ログインページにアクセスすると" do
    context '未ログインの場合' do
      it "リクエストが成功すること。" do
        get new_worker_user_session_path
        expect(response).to have_http_status(200)
      end
    end

    context 'ログイン済みの場合' do
      before do
        user = FactoryBot.create(:worker_user)
        sign_in user
      end

      it "ユーザーページにリダイレクトされること。" do
        get new_worker_user_session_path
        expect(response).to have_http_status(302)
      end
    end
  end

  # describe "会員登録ページにアクセスすると" do
  #   it "リクエストが成功すること。" do
  #     get new_worker_user_registration_path
  #     expect(response).to have_http_status(200)
  #   end
  # end
end
```
factorys/worker_users.rb
```
# frozen_string_literal: true

FactoryBot.define do
  factory :worker_user do
    sei { 'サンプル'}
    mei { '太郎'}
    sequence(:email)    { |n| "sample#{n}@example.com" }
    password { 'pasword' }
    confirmed_at { Date.today }
  end
end
```

spec/rails_helper.rb
```
# This file is copied to spec/ when you run 'rails generate rspec:install'
require 'spec_helper'
ENV['RAILS_ENV'] ||= 'test'

require File.expand_path('../config/environment', __dir__)

# Prevent database truncation if the environment is production
abort("The Rails environment is running in production mode!") if Rails.env.production?
require 'rspec/rails'
# Add additional requires below this line. Rails is not loaded until this point!

# Requires supporting ruby files with custom matchers and macros, etc, in
# spec/support/ and its subdirectories. Files matching `spec/**/*_spec.rb` are
# run as spec files by default. This means that files in spec/support that end
# in _spec.rb will both be required and run as specs, causing the specs to be
# run twice. It is recommended that you do not name files matching this glob to
# end with _spec.rb. You can configure this pattern with the --pattern
# option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
#
# The following line is provided for convenience purposes. It has the downside
# of increasing the boot-up time by auto-requiring all files in the support
# directory. Alternatively, in the individual `*_spec.rb` files, manually
# require only the support files necessary.
#
Dir[Rails.root.join('spec', 'support', '**', '*.rb')].each { |f| require f }

# Checks for pending migrations and applies them before tests are run.
# If you are not using ActiveRecord, you can remove these lines.
begin
  ActiveRecord::Migration.maintain_test_schema!
rescue ActiveRecord::PendingMigrationError => e
  puts e.to_s.strip
  exit 1
end
RSpec.configure do |config|
  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
  config.fixture_path = "#{::Rails.root}/spec/fixtures"

  # If you're not using ActiveRecord, or you'd prefer not to run each of your
  # examples within a transaction, remove the following line or assign false
  # instead of true.
  config.use_transactional_fixtures = true

  # RSpec Rails can automatically mix in different behaviours to your tests
  # based on their file location, for example enabling you to call `get` and
  # `post` in specs under `spec/controllers`.
  #
  # You can disable this behaviour by removing the line below, and instead
  # explicitly tag your specs with their type, e.g.:
  #
  #     RSpec.describe UsersController, :type => :controller do
  #       # ...
  #     end
  #
  # The different available types are documented in the features, such as in
  # https://relishapp.com/rspec/rspec-rails/docs
  config.infer_spec_type_from_file_location!

  config.include RequestSpecHelper, type: :request
  config.include Devise::Test::IntegrationHelpers, type: :system
  
  # Filter lines from Rails gems in backtraces.
  config.filter_rails_from_backtrace!
  # arbitrary gems may also be filtered via:
  # config.filter_gems_from_backtrace("gem name")
end
```

Gemfile
```
# frozen_string_literal: true

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby '2.6.3'
gem 'bootsnap', '>= 1.1.0', require: false
gem 'coffee-rails', '~> 4.2'
gem 'jbuilder', '~> 2.5'
gem 'pg', '>= 0.18', '< 2.0'
gem 'puma', '~> 3.11'
gem 'rails', '~> 5.2.3'
gem 'sass-rails', '~> 5.0'
gem 'turbolinks', '~> 5'
gem 'uglifier', '>= 1.3.0'

group :development, :test do
  gem 'byebug', platforms: %i[mri mingw x64_mingw]
end

group :development do
  gem 'factory_bot_rails', '~> 5.1'
  gem 'listen', '>= 3.0.5', '< 3.2'
  gem 'rspec-rails'
  gem 'rubocop', '~> 0.76.0'
  gem 'rubocop-performance', '~> 1.5'
  gem 'spring', '~> 2.1'
  gem 'spring-watcher-listen', '~> 2.0.0'
  gem 'web-console', '>= 3.3.0'
end

group :test do
  gem 'capybara', '>= 2.15'
  gem 'chromedriver-helper'
  gem 'selenium-webdriver'
end

gem 'tzinfo-data', platforms: %i[mingw mswin x64_mingw jruby]

gem 'acts-as-taggable-on', '~> 6.0'
gem 'carrierwave', '1.2.2'
gem 'devise'
gem 'faker'
gem 'html2slim'
gem 'i18n', '~> 1.7'
gem 'mini_magick', '4.7.0'
gem 'omniauth-facebook'
gem 'ransack', '~> 2.3'
gem 'slim-rails', '3.1.3'
gem 'kaminari', '>= 1.1.1'
```

###試したこと
コンソール似て、FactoryBot.createを実行してみました。

```
irb(main):001:0> FactoryBot.create(:worker_user)
```
すると、正常にユーザーを作成することができました。

###補足情報（FW/ツールのバージョンなど）
ruby 2.6.2
rails 5.2.3
macOS 10.14.6