undefined methodのエラーに関しての質問です！

#解決したいこと
下記のエラーを解消して、youtubeの動画を投稿できるようにしたいです。カラムにyoutube_urlは定義してあるのでなぜエラーになるのかわかりません！

Started PUT "/__web_console/repl_sessions/db9f799215cc6c438ac454364e2c021f" for ::1 at 2019-12-19 10:38:03 +0900
Started PUT "/__web_console/repl_sessions/db9f799215cc6c438ac454364e2c021f" for ::1 at 2019-12-19 10:38:06 +0900
Started GET "/admin/articles/new" for ::1 at 2019-12-19 10:51:08 +0900
   (0.2ms)  SELECT sqlite_version(*)
Processing by Admin::ArticlesController#new as HTML
  Member Load (1.7ms)  SELECT "members".* FROM "members" WHERE "members"."id" = ? LIMIT ?  [["id", 1], ["LIMIT", 1]]
  ↳ app/controllers/application_controller.rb:4:in `current_member'
  Rendering admin/articles/new.html.erb within layouts/application
  Rendered shared/_errors.html.erb (Duration: 2.1ms | Allocations: 178)
  Rendered admin/articles/_form.html.erb (Duration: 10.4ms | Allocations: 2231)
  Rendered admin/articles/new.html.erb within layouts/application (Duration: 14.7ms | Allocations: 2694)
Completed 500 Internal Server Error in 33ms (ActiveRecord: 1.7ms | Allocations: 5065)


  
ActionView::Template::Error (undefined method `youtube_url' for #<Article:0x00007fa285c73768>):
     7:   </tr>
     8:   <tr>
     9:     <th><%= form.label :youtube_url %></th>
    10:     <td><%= form.url_field :youtube_url, size: 20 %></td>
    11:   </tr>
    12:   <tr>
    13:     <th><%= form.label :body %></th>
  
app/views/admin/articles/_form.html.erb:10
app/views/admin/articles/new.html.erb:5
app/views/admin/articles/new.html.erb:4

form関連

erb
1<%= form_for [:admin,@article] do |form|%>
2    <%= render "form", form: form %>
3    <div><%= form.submit %></div>
4<%end%>

erb
1<tr>
2    <th><%= form.label :youtube_url %></th>
3    <td><%= form.url_field :youtube_url, size: 20 %></td>
4  </tr>

コントローラー

rb
1class Admin::ArticlesController < Admin::Base
2    
3
4    def index
5        @articles = Article.order(released_at: :desc).page(params[:page]).per(5)
6    end
7
8    def show
9        @article = Article.find(params[:id])
10    end
11
12    def new
13        @article = Article.new
14    end
15
16    def edit
17        @article = Article.find(params[:id])
18    end
19
20    def create
21        @article = Article.new(article_params)
22
23        url = params[:article][:youtube_url]
24        url = url.last(11)
25        @article.youtube_url = url
26        
27        if @article.save
28            redirect_to [:admin, @article], notice: "ニュースを登録しました"
29        else
30         render "new"
31        end
32    end
33    
34    def update
35        @article = Article.find(params[:id])
36        @article.assign_attributes(article_params)
37        if @article.save
38            redirect_to [:admin, @article], notice: "ニュースを更新しました。"
39        else
40            render "edit"
41        end
42    end
43
44    def destroy
45        @article = Article.find(params[:id])
46        @article.destroy
47        redirect_to :admin_articles
48    end
49
50    private def article_params
51        params.required(:article).permit(
52          :title,
53          :body,
54          :released_at,
55          :no_expiration,
56          :expired_at,
57          :member_only
58        )
59      end
60end

rb
1create_table "articles", force: :cascade do |t|
2    t.string "title", null: false
3    t.text "body", null: false
4    t.datetime "released_at", null: false
5    t.datetime "expired_at"
6    t.boolean "member_only", default: false, null: false
7    t.datetime "created_at", precision: 6, null: false
8    t.datetime "updated_at", precision: 6, null: false
9    t.string "youtube_url"
10  end