タグ機能実装でpost時にNoMethodError

Question

前提・実現したいこと

こちらを参考にタグ機能を実装していったところ、エラーが発生しました。

発生している問題・エラーメッセージ

ブラウザ上でtitleとcontentのみを入力した場合はpostは成功します。taglistに一文字でも入力するとエラーが出るといった感じです。また、何も入力しなくてもpostは成功します。

NoMethodError (undefined method `[]=' for nil:NilClass):

app/controllers/posts_controller.rb:30:in `create'

undefined method `[]=' for nil:NilClass

ソースコード

posts_controller.rb

class PostsController < ApplicationController
  before_action :set_post, only: [:show, :edit, :update, :destroy]

  # GET /posts
  # GET /posts.json
  def index
    @posts = Post.all
    @tags = Post.tag_counts_on(:tags).most_used(20)
  end

  # GET /posts/1
  # GET /posts/1.json
  def show
  @post = Post.find(params[:id])
  @tags = @post.tag_counts_on(:tags)
  end

  # GET /posts/new
  def new
    @post = Post.new
  end

  # GET /posts/1/edit
  def edit
  end

  # POST /posts
  # POST /posts.json
  def create
    @post = Post.new(post_params)

    respond_to do |format|
      if @post.save
        format.html { redirect_to @post, notice: 'Post was successfully created.' }
        format.json { render :show, status: :created, location: @post }
      else
        format.html { render :new }
        format.json { render json: @post.errors, status: :unprocessable_entity }
      end
    end
  end

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

  # DELETE /posts/1
  # DELETE /posts/1.json
  def destroy
    @post.destroy
    respond_to do |format|
      format.html { redirect_to posts_url, notice: 'Post was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

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

    # Only allow a list of trusted parameters through.
    def post_params
      params.require(:post).permit(:title, :content, :tag_list)
    end
end

post.rb

class Post < ApplicationRecord
    acts_as_taggable
    acts_as_taggable_on :skills, :interests
end

_form.html.erb

<%= form_with(model: post) do |form| %>
  <% if post.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(post.errors.count, "error") %> prohibited this post from being saved:</h2>

      <ul>
        <% post.errors.each do |error| %>
          <li><%= error.full_message %></li>
        <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= form.label :title %>
    <%= form.text_field :title %>
  </div>

  <div class="field">
    <%= form.label :content %>
    <%= form.text_area :content %>
  </div>

  <div class="field">
    <%= form.label :tag_list %>
    <%= form.text_area :tag_list, value: @post.tag_list.join(',') %>
  </div>

  <% tag.each do |tag| %>
   <%= form.check_box :tag_list, { multiple: true }, "#{tag.name}", nil %>
   <%= form.label " #{tag.name}(#{tag.taggings_count})"%>
  <% end %>

  <div class="actions">
    <%= form.submit %>
  </div>
<% end %>

gemfile

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby '2.7.2'
gem 'acts-as-taggable-on'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 6.1.0'
# Use sqlite3 as the database for Active Record
gem 'sqlite3', '~> 1.4'
# Use Puma as the app server
gem 'puma', '~> 5.0'
# Use SCSS for stylesheets
gem 'sass-rails', '>= 6'
# Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
gem 'webpacker', '~> 5.0'
# 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', '~> 2.7'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 4.0'
# Use Active Model has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Active Storage variant
# gem 'image_processing', '~> 1.2'

# Reduces boot times through caching; required in config/boot.rb
gem 'bootsnap', '>= 1.4.4', require: false

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]
end

group :development do
  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
  gem 'web-console', '>= 4.1.0'
  # Display performance information such as SQL time and flame graphs for each request in your browser.
  # Can be configured to work on production as well see: https://github.com/MiniProfiler/rack-mini-profiler/blob/master/README.md
  gem 'rack-mini-profiler', '~> 2.0'
end

group :test do
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '>= 3.26'
  gem 'selenium-webdriver'
  # Easy installation and use of web drivers to run system tests with browsers
  gem 'webdrivers'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

試したこと

gemfileでバージョンを指定していないのが原因かと思い指定してみたところこのようなエラーが出てきたため戻しました。

gem 'acts-as-taggable-on', '~> 6.0'

Fetching gem metadata from https://rubygems.org/.............
Fetching gem metadata from https://rubygems.org/.
Resolving dependencies...
Bundler could not find compatible versions for gem "activerecord":
  In snapshot (Gemfile.lock):
    activerecord (= 6.1.0)

  In Gemfile:
acts-as-taggable-on (~> 6.0) x64-mingw32 was resolved to 6.0.0, which
depends on
      activerecord (~> 5.0) x64-mingw32

    rails (~> 6.1.0) x64-mingw32 was resolved to 6.1.0, which depends on
      activerecord (= 6.1.0) x64-mingw32

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.

補足情報（FW/ツールのバージョンなど）

Windows10
ruby 2.7.2p137
Rails 6.1.0

Answer 1

app/controllers/posts_controller.rb:30:in `create'

この30行目とはどこのことになりますか？

おそらく、@postが空の場合の条件分岐が無いことが原因な気がしています。

Comments

[sorata_toll]

@post = Post.new(post_params)
こちらが30行目です。因みにブラウザ上でtitleとcontentのみを入力した場合はpostは成功します。taglistに一文字でも入力するとエラーが出るといった感じです。よろしくお願いします。

[educ_gt]

binding.pryでparamsの中身をみるとどのような形になっていますか？

[sorata_toll]

Started POST "/posts" for ::1 at 2020-12-31 21:51:31 +0900
Processing by PostsController#create as HTML
Parameters: {"authenticity_token"=>"[FILTERED]", "post"=>{"title"=>"g", "content"=>"g", "tag_list"=>"g"}, "commit"=>"Create Post"}

From: C:/Users/hoge/Desktop/blog8/app/controllers/posts_controller.rb:30 PostsController#create:

29: def create
=> 30: binding.pry
31: @post = Post.new(post_params)
32:
33:
34: respond_to do |format|
35: if @post.save
36: format.html { redirect_to @post, notice: 'Post was successfully created.' }
37: format.json { render :show, status: :created, location: @post }
38: else
39: format.html { render :new }
40: format.json { render json: @post.errors, status: :unprocessable_entity }
41: end
42: end
43: end
[1] pry(#<PostsController>)>

こちらでしょうか？

[educ_gt]

ありがとうございます。
paramsには問題なさそうですね。

bundle list acts-as-taggable-on
とするとどのような結果が出力されますか？

[sorata_toll]

> bundle list acts-as-taggable-on
ERROR: "bundle.cmd list" was called with arguments ["acts-as-taggable-on"]
Usage: "bundle.cmd list"

とでてきました

[educ_gt]

なるほどです。なにかはねられてますね。。
アプリディレクトリでbundle list もエラーでますか？

[sorata_toll]

> bundle list
Gems included by the bundle:
* actioncable (6.1.0)
* actionmailbox (6.1.0)
* actionmailer (6.1.0)
* actionpack (6.1.0)
* actiontext (6.1.0)
* actionview (6.1.0)
* activejob (6.1.0)
* activemodel (6.1.0)
* activerecord (6.1.0)
* activestorage (6.1.0)
* activesupport (6.1.0)
* acts-as-taggable-on (5.0.0)
* addressable (2.7.0)
* bindex (0.8.1)
* bootsnap (1.5.1)
* builder (3.2.4)
* byebug (11.1.3)
* capybara (3.34.0)
* childprocess (3.0.0)
* coderay (1.1.3)
* concurrent-ruby (1.1.7)
* crass (1.0.6)
* erubi (1.10.0)
* ffi (1.14.2)
* globalid (0.4.2)
* i18n (1.8.5)
* jbuilder (2.10.1)
* loofah (2.8.0)
* mail (2.7.1)
* marcel (0.3.3)
* method_source (1.0.0)
* mimemagic (0.3.5)
* mini_mime (1.0.2)
* mini_portile2 (2.4.0)
* minitest (5.14.2)
* msgpack (1.3.3)
* nio4r (2.5.4)
* nokogiri (1.10.10)
* pry (0.13.1)
* pry-rails (0.3.9)
* public_suffix (4.0.6)
* puma (5.1.1)
* rack (2.2.3)
* rack-mini-profiler (2.3.0)
* rack-proxy (0.6.5)
* rack-test (1.1.0)
* rails (6.1.0)
* rails-dom-testing (2.0.3)
* rails-html-sanitizer (1.3.0)
* railties (6.1.0)
* rake (13.0.3)
* regexp_parser (1.8.2)
* rubyzip (2.3.0)
* sass-rails (6.0.0)
* sassc (2.4.0)
* sassc-rails (2.1.2)
* selenium-webdriver (3.142.7)
* semantic_range (2.3.1)
* sprockets (4.0.2)
* sprockets-rails (3.2.2)
* sqlite3 (1.4.2)
* thor (1.0.1)
* tilt (2.0.10)
* turbolinks (5.2.1)
* turbolinks-source (5.2.0)
* tzinfo (2.0.4)
* tzinfo-data (1.2020.5)
* web-console (4.1.0)
* webdrivers (4.4.2)
* webpacker (5.2.1)
* websocket-driver (0.7.3)
* websocket-extensions (0.1.5)
* xpath (3.2.0)
* zeitwerk (2.4.2)
Use `bundle info` to print more detailed information about a gem
特にエラーはないかと思います

[educ_gt]

acts-as-taggable-on (5.0.0)

このバージョンが怪しそうなので、

gem 'acts-as-taggable-on', '~> 6.0'　

を再度指定して、gemfile.lockを一度削除して、再度bundle installする。

だめなら
gem 'acts-as-taggable-on', '~> 7.0'

にして、再度gemfile.lockを削除してbundle install　こちらでいかがでしょうか。

[sorata_toll]

6の指定ではできませんでしたが、7を指定することで無事解決することができました！
ありがとうございました！