Проблема показа ника пользователя в комментариях в блоге на Rails?

Когда я хочу создать коментарий под постом, в блоге и чтоб там выводился ник пользователя, но выводится такая ошибка

NoMethodError in Posts#show
Showing /home/ali/Рабочий стол/relsa/app/views/posts/show.html.erb where line #31 raised:

undefined method `user' for nil:NilClass
Extracted source (around line #31):

  <% @post.comments.each do |comment| %>
  <div class="alert alert-light">
       <p>Пользователь <%=@comments.user.username%></p>
   <p><strong><%=comment.username%></strong> <br> <%=comment.body%> <%= image_tag comment.image.url(:thumb), class: 'img-show' if comment.image? %> </p>

Вот код show.html.erb

<% if user_signed_in? %>
    <span>Здравствуйте, <%= current_user.username %></span>
    <%= link_to 'Выйти', destroy_user_session_path, :method => :delete %>
<% else %>
    <%= link_to 'Войти', new_user_session_path %> или <%= link_to 'Зарегистрироваться', new_user_registration_path %>
<% end %>
    <%=link_to "Главная страница", home_path %> &nbsp; &nbsp;
    <%=link_to "Добавления статьи", new_post_path %>

<h3>Пользователь <%=@post.user.username%></h3>
<h1><%=@post.title %> </h1>

<p><%=@post.body %></p>

<p>
 <%= image_tag @post.image.url(:thumb), class: 'img-show' if @post.image? %>
</p>    
<hr>


<% if user_signed_in? && @post.user==current_user %>
<%= link_to "Редактировать", edit_post_path(@post), :class=> 'btn btn-warning' %>
<%= link_to "Удалить пост", post_path(@post), method: :delete, data: {confirm:"Вы хотите удалить статью  ?"}, :class => 'btn btn-danger'%>

   <%end%>  
  <% if @post.comments.size > 0 %>
     <h2>Вcе коментарии  <%=@post.comments.count %> </h2> 
     <% end %>
  <% @post.comments.each do |comment| %>
  <div class="alert alert-light">
       <p>Пользователь <%=@comments.user.username%></p>
   <p><strong><%=comment.username%></strong> <br> <%=comment.body%> <%= image_tag comment.image.url(:thumb), class: 'img-show' if comment.image? %> </p>  
  </div>
   <% if user_signed_in? %>
  <%= link_to "Удалить Коммент", post_comment_path(@post, comment), method: :delete, data: { confirm: "Вы хотите удалить?" }, :class => 'btn btn-danger'%>
 <%= link_to "Редактировать комент", edit_post_comment_path(@post, comment), :class=> 'btn btn-warning' %>

  <% end %>  
    <% end %>       

<% if user_signed_in? %>
 <%=form_for([@post, @post.comments.build]) do |f| %>
 <p>
  Пользователь<br>
    <%=f.text_field(:username)%>
 </p>

 <p>
   Текст комментария<br>
    <%= f.text_area(:body)%>
  </p>

Код comments_controller.rb

class CommentsController < ApplicationController
    before_action :authenticate_user!, except: [:index, :show]
    def create
    @post=Post.find(params[:post_id])   
     @comments.user_id = current_user.id

    @comments=@post.comments.create(comment_params)
    redirect_to post_path(@post)
    end
    def destroy
  @post = Post.find(params[:post_id])
  @post.comments.find(params[:id]).destroy
  redirect_to post_path(@post)
end

def update
@post = Post.find(params[:post_id])
@comment = @post.comments.find(params[:id])

if (@comment.update(comment_params))
redirect_to post_path(@post)
else
render 'edit'
end
end


  def edit
 @post = Post.find(params[:post_id]) 
  @comment = @post.comments.find(params[:id])
  end 

    private def comment_params 
     params.require(:comment).permit(:username, :body, :image)  
end
end

comment.rb

class Comment < ApplicationRecord
 mount_uploader :image, ImageUploader
 validates:username, presence:true, length:{minimum:5}
 validates:body, presence:true, length:{minimum:5}
  belongs_to :post
  belongs_to :user
end

user.rb

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable,:confirmable, :validatable
         has_many :posts 
         has_many :comments
       validates :username, presence: :true, uniqueness: { case_sensitive: false }
end

schema.rb

ActiveRecord::Schema.define(version: 2019_03_23_152808) do

  create_table "comments", force: :cascade do |t|
    t.string "username"
    t.text "body"
    t.integer "post_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "image"
    t.integer "user_id"
    t.index ["post_id"], name: "index_comments_on_post_id"
  end

  create_table "posts", force: :cascade do |t|
    t.string "title"
    t.text "body"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "image"
    t.integer "user_id"
  end

  create_table "users", force: :cascade do |t|
    t.string "email", default: "", null: false
    t.string "encrypted_password", default: "", null: false
    t.string "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.string "confirmation_token"
    t.datetime "confirmed_at"
    t.datetime "confirmation_sent_at"
    t.string "unconfirmed_email"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "username"
    t.index ["confirmation_token"], name: "index_users_on_confirmation_token", unique: true
    t.index ["email"], name: "index_users_on_email", unique: true
    t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
    t.index ["username"], name: "index_users_on_username", unique: true
  end

end