投稿にタグ付け　uninitialized constant Post::TagRelationship

前提・実現したいこと

現在SNSのようなアプリケーションを作っていて
投稿にタグ付けをできるように追加実装しています。

https://qiita.com/E6YOteYPzmFGfOD/items/bfffe8c3b31555acd51d

こちらの記事を参考に実装を進めていたのですが、

発生している問題・エラーメッセージ

NameError in Posts#index
Showing /Users/mono/projects/rank_top/app/views/posts/index.html.erb where line #47 raised:

uninitialized constant Post::TagRelationship
Extracted source (around line #47):
45　 </div>
46
47　 <% post.tags.each do |tag| %>
48　　　<%= tag.tag_name %>49
50　 <% end %>

のようなエラーが出てしまい

中間テーブルやアソシエーションに問題があると仮説を立てて解決しようとしましたが
解決法が分からず実装が止まってしまいました。

該当のソースコード

tag_relationship.rb

class TagReletionship < ApplicationRecord
  belongs_to :post
  belongs_to :tag
end

post.rb

class Post < ApplicationRecord

has_many  :tag_relationship, dependent: :destroy
has_many  :tags, through: :tag_relationship

end

tag.rb

class Tag < ApplicationRecord
  has_many :tag_relationsship, dependent: :destroy
  
  has_many :posts, through: :tag_relationship

  validates :tag_name, uniqueness: true
end

routes.rb

Rails.application.routes.draw do
  devise_for :users
  root to: 'posts#index'

  resources :users, only: :show

  resources :posts do
    resources :comments, only: :create
    resource :likes, only: [:create, :destroy]
    collection do
      get 'search'
    end
  end
  
end


posts.index.html.erb

<%= form_with url: search_posts_path, method: :get, local: true do |form| %>
  <%= form.text_field :keyword, placeholder: "投稿を検索する", class: "search-input" %>
  <%= form.submit "検索", class: "search-btn" %>
<% end %>

<div class="row row-cols md-3">
<% @posts.each do |post| %>
  <div class="card d-flex justify-content-around m-5" style="width: auto; heigth: auto;">
  <div class="card-body border border-primary">
  
  
    <%= image_tag post.image, :width => '280', :height => '280'  if post.image.attached? %>
    
    
      <h4 class="card-title"><%= post.title %></h4>
      １位<p class="card-text"><%= post.rank1 %></p>
      ２位<p class="card-text"><%= post.rank2 %></p>
      ３位<p class="card-text"><%= post.rank3 %></p>

             
    

    <div class="btn-group">
          <button type="button" class="btn btn-5m btn-outline-secondary">
            <%= link_to '詳細', post_path(post.id) , method: :get %></button>
          <button type="button" class="btn btn-5m btn-outline-secondary">
            <%=link_to post.user.name, user_path(post.user.id)%></button>
    </div>


    <div id="likes_buttons_<%= post.id %>">
      <%= render partial: 'likes/like', locals: { post: post} %>
    </div>



    
      <p class="card-text">
        <small class="text-muted"><%= post.updated_at %>
        </small>
      </p>


  </div>
  </div>
 
      <% post.tags.each do |tag| %>
        <%= tag.tag_name %>
      <% end %>

   <% end %>
    
  </div>


posts_contoroller.rb

class PostsController < ApplicationController
  before_action :authenticate_user!, except: [:index, :show, :search]
  before_action :move_to_index, except: [:index, :show, :search]

  def index
    @posts = Post.includes(:user).order('created_at DESC')
    @likes = Like.where(user_id: current_user)
  end

  def new
    @post = Post.new
  end

  def create
    @post = Post.new(post_params)
    tag_list = params[:post][:tag_name].split(',')
    @post.likes_count = (0)
    if @post.save
      redirect_to root_path
    else
      render :new
    end
  end

  def show
    @post = Post.find(params[:id])
    @comment = Comment.new
    @comments = @post.comments.includes(:user)
  end

  def edit
    @post = Post.find(params[:id])
    @tag_list =@post.tags.pluck(:name).join(",")
  end

  def update
    @post = Post.find(params[:id])
    tag_list = params[:post][:tag_ids].split(',')
    if @post.update(post_params)
      @post.save_tags(tag_list)
      redirect_to root_path
    else
      render :edit
    end
  end

  def destroy
    post = Post.find(params[:id])
    post.destroy
    redirect_to root_path
  end

  def search
    @posts =Post.search(params[:keyword])
    return nil if params[:input] == ""
    tag = Tag.where(['tag_name LIKE ?',  "%#{params[:input]}%"])
  end

  private

  def post_params
    params.require(:post).permit(:title, :rank1, :rank2, :rank3, :image, :likes_count).merge(user_id: current_user.id)
  end

  def move_to_index
    unless user_signed_in?
      redirect_to action: :index
    end
  end

end