Undefined method `id' for nil:NilClass (Controller#create) - ruby-on-rails

Question

NameError in CommentsController#create undefined method `id' for nil:NilClass
The error on the following line. I want to save in field user_id (comment table) id user, which authorized in current time:
update_column(:user_id, user.id)
Model
class Comment < ActiveRecord::Base
belongs_to :user
has_many :likes
after_save :update_comments
def update_comments
update_column(:user_id, user.id)
true
end
end
class User < ActiveRecord::Base
validates :name, presence: true, uniqueness: true
has_secure_password
has_many :comments
end
Comments_controller.rb
def create
#user = User.all
#comment = Comment.all
#comment = Comment.new(comment_params)
respond_to do |format|
if #comment.save
format.html { redirect_to #comment, notice: 'Comment was successfully created.' }
format.json { render action: 'show', status: :created, location: #comment }
else
format.html { render action: 'new' }
format.json { render json: #comment.errors, status: :unprocessable_entity }
end
end
end
**view/_form**
<%= simple_form_for(#comment) do |f| %>
<%= f.error_notification %>
<div class="form-inputs">
<%= f.input :text %>
</div>
<div class="form-actions">
<%= f.button :submit %>
</div>
<% end %>
sessions/new
<%= form_tag do %>
<div class="as"><% if flash[:alert] %>
<p id="notice"><%= flash[:alert] %></p>
<% end %></div>
<br><br>
<fieldset>
<legend></legend>
<dl>
<dt><label for="email">Log in:</label></dt>
<dd><%= text_field_tag :name, params[:name], class: "user" %></dd>
</dl>
<dl>
<dt><label for="password">Password:</label></dt>
<dd><%= password_field_tag :password, params[:password], class: "password" %></dd>
</dl>
</fieldset>
<fieldset class="action">
<input type="submit" name="submit" id="submit" value="Enter" />
</fieldset>
<% end %>

Answer 1

Try using
def create
#user = User.all
#comment = Comment.all
#comment = #current_user.comments.new(comment_params)
respond_to do |format|
if #comment.save
format.html { redirect_to #comment, notice: 'Comment was successfully created.' }
format.json { render action: 'show', status: :created, location: #comment }
else
format.html { render action: 'new' }
format.json { render json: #comment.errors, status: :unprocessable_entity }
end
end
end
Then you need not to explicitly assign user_id to comment after_create. Using association it will automaticlly assign the user_id to the comment.