入力フォーム追加•削除機能でのエラー”undefined method `new

プログラミング初心者です。現在、RubyonRailsにてwebアプリ作成中です。

gem 'cocoon'

を利用し、入力フォームの追加・削除の実装をしているのですが下記エラーが出てしまい
解決できずにいるのでお力をお貸しいただけたらと思い質問させていただきます。

前提

親　User
子　Post・Item

エラーメッセージ

NoMethodError in Posts#new
Showing /myapp/app/views/items/_items_fields.html.erb where line #33 raised:

undefined method `new_record?' for nil:NilClass
Extracted source (around line #33):
31　　　　</div>
32　　　　<!-- 削除ボタン -->
33　　　　<%= link_to_remove_association "削除", f %>
34　　　　<% end %>
35　　　　</td>
36　　　　</tr>
             
Trace of template inclusion: #<ActionView::Template app/views/posts/new.html.erb locals=[]>

Rails.root: /myapp

Application Trace | Framework Trace | Full Trace
app/views/items/_items_fields.html.erb:33
app/views/items/_items_fields.html.erb:7
app/views/posts/new.html.erb:15
app/views/posts/new.html.erb:14
app/views/posts/new.html.erb:5

該当のソースコード

html
1**post/new.html.erb**
2
3<div class="main posts-new">
4  <div class="container">
5    <h1 class="form-heading">投稿画面</h1>
6
7    <%= form_with(model: @user, local: true) do |s| %>
8      <p>メイン写真</p>
9      <label for="file_photo">
10        <%= s.label :image_photo %>
11        <input name="image_photo" type="file" id="file_photo" >
12      </label>
13      <%= s.text_field :image_title %>
14      <%= s.text_field :description %>
15      <div class="parents">
16          <%= s.fields_for :items do |t| %>
17              <%= render "items/items_fields", f: t %>
18          <% end %>
19          <div class="links">
20            <%= link_to_add_association "追加", s, :items %>
21          </div>
22        </div>
23        <div class="actions">
24          <input type="submit" value="投稿">
25        </div>
26    <% end %>
27    
28    <%= link_to("トップページへ戻る", "/") %>
29  </div>
30</div>

html
1**items/_item.fields.html.erb**
2
3<div class="nested-fields">
4  <table>
5    <tr>
6      <td class="td-fixed-select">
7
8        <%= f.fields_for :items do |t| %>
9        <div class="msr_file_05">
10          <p>アイテム写真</p>
11          <label for="file_photo">
12            画像を選択してください
13            <%= f.label :item_image %>
14             <input name="item_image" type="file" id="file_photo" >
15          </label>
16        </div>
17        <div class="msr_text_05">
18          <label>商品名</label>
19          <%= f.text_field :products_name %>
20        </div>
21        <div class="msr_text_05">
22          <label>ブランド</label>
23          <%= f.text_field :brand %>
24        </div>
25        <div class="msr_text_05">
26          <label>サイズ</label>
27          <%= f.text_field :size %>
28        </div>
29        <div class="msr_text_05">
30          <label>価格</label>
31          <%= f.text_field :price %>
32        </div>
33        <!-- 削除ボタン -->
34        <%= link_to_remove_association "削除", f %>
35        <% end %>
36      </td>
37    </tr>
38  </table>
39</div>

html
1**users_controller**
2
3class UsersController < ApplicationController
4  before_action :logged_in_user, only:[:destroy]
5
6  def index
7    @users = User.all
8  end
9
10  def show
11    @user = User.find_by(id: params[:id])
12  end
13
14  def new
15    @user = User.new
16    @post = @user.post.build
17    @item = @post.item.build
18  end
19
20  def create
21    @user = User.new(user_params)
22    if @user.save
23      session[:user_id] = @user.id
24      flash[:notice] = "ユーザー登録が完了しました"
25      redirect_to("/users/#{@user.id}")
26    else
27      render("users/new")
28    end
29  end
30
31  def edit
32    @user = User.find_by(id: params[:id])
33  end
34
35  def update
36    @user = User.find_by(id: params[:id])
37    @user.name = params[:name]
38    @user.email = params[:email]
39    @user.password = params[:password]
40    if @user.save
41      flash[:notice] = "ユーザー情報を編集しました"
42      redirect_to("/users/#{@user.id}")
43    else
44      render("users/edit")
45    end
46  end
47  
48  private
49def user_params
50      params.require(:user).permit(:name, :email, :password, post_attributes: [:id, :image_title, :description, item_attributes: [:id, :item_image, :products_name, :brand, :size, :price]])
51end
52end

html
1**post_controller**
2class PostsController < ApplicationController
3  before_action :ensure_correct_user, {only: [:edit, :update, :destroy]}
4  def index
5    @posts = Post.all.order(created_at: :desc)
6  end
7
8  def show
9    @post = Post.find_by(id: params[:id])
10    @user = @post.user
11  end
12
13  def new
14    @post = Post.new
15  end
16
17  def create
18    @post = Post.new(image_title: params[:image_title], description: params[:description],products_name: params[:products_name], brand: params[:brand], size: params[:size], price: params[:price])
19    @post.user_id = @current_user.id
20    if @post.save
21      @post.image_photo="#{@post.id}.jpg"
22      image=params[:image_photo]
23      File.binwrite("app/assets/images/posts/#{@post.image_photo}", image.read)
24      redirect_to("/posts/#{@post.id}")
25    else
26      render("/posts/new")
27    end
28
29
30  end
31
32  def edit
33    @post = Post.find_by(id: params[:id])
34  end
35
36  def update
37    @post = Post.find_by(id: params[:id])
38    @post.image_title = params[:image_title]
39    @post.price = params[:price]
40    @post.image_photo="#{@post.id}.jpg"
41    image=params[:image_photo]
42    File.binwrite("app/assets/images/posts/#{@post.image_photo}", image.read)
43    if @post.save
44      redirect_to("/posts/#{@post.id}")
45    else
46      render("posts/#{@post.id}/edit")
47    end
48  end
49
50  def destroy
51    @post = Post.find_by(id: params[:id])
52    @post.destroy
53    redirect_to("/")
54  end
55
56  def ensure_correct_user
57    @post = Post.find_by(id: params[:id])
58    if @post.user_id != @current_user.id
59      flash[:notice] = "権限がありません"
60      redirect_to("/posts/index")
61    end
62  end
63end

html
1class Post < ApplicationRecord
2  belongs_to :user
3  has_many :items, dependent: :destroy
4  accepts_nested_attributes_for :items, allow_destroy: true
5
6  validates :user_id, {presence: true}
7
8  def user
9    return User.find_by(id: self.user_id)
10  end
11end

html
1class User < ApplicationRecord
2  has_secure_password
3  has_many :posts, dependent: :destroy
4  accepts_nested_attributes_for :posts, allow_destroy: true
5  
6
7  validates :name, {presence: true}
8  validates :email, {presence: true, uniqueness: true}
9
10  def posts
11    return Post.where(user_id: self.id)
12  end
13end
14