undefined method `count' for nil:NilClass rails - ruby-on-rails

Question

I am trying to have a photo upload section in my room listing. when I try to click on the photos I get this error
undefined method 'count' for nil:NilClass rails <% if #photos.count > 0 %> .
I have added a photo_upload.html.erb page and a _room_menu partial but still I get the error.
here's my code:
photos_controller.rb
class PhotosController < ApplicationController
def create
#room = Room.find(params[:room_id])
if params[:images]
params[:images].each do |img|
#room.photos.create(image:img)
end
#photos = #room.photos
redirect_back(fallback_location:request.referer, notice: "Saved...")
end
end
end
**views/rooms/photo_upload.html.erb**
<div class="row">
<div class="col-md-3">
<%= render 'room_menu' %>
</div>
<div class="col-md-9">
<div class="panel panel-default">
<div class="panel-heading">
Photos
</div>
<div class="panel-body">
<div class="container">
<div class="row">
<div class="col-md-offset-3 col-md-6">
<!-- PHOTOS UPLOAD GOES HERE -->
<%= form_for #room, url: room_photos_path(#room), method: 'post', html: {multipart: true} do |f| %>
<div class="row">
<div class="form-group">
<span class="btn btn-default btn-file text-babu">
<i class="fa fa-cloud-upload" aria-hidden="true"></i> Select Photos
<%= file_field_tag "images[]", type: :file, multiple: true %>
</span>
</div>
</div>
<div class="text-center">
<%= f.submit "Add Photos", class: "btn btn-form" %>
</div>
<% end %>
</div>
</div>
<div id="photos"><%= render 'photos/photos_list' %></div>
</div>
</div>
</div>
</div>
</div>
views/rooms/_room_menu.html.erb
<ul class="sidebar-list">
<li class="sidebar-item">
<%= link_to "Listing", listing_room_path, class: "sidebar-link active" %>
<span class="pull-right text-babu"><i class="fa fa-check"></i></span>
</li>
<li class="sidebar-item">
<%= link_to "Pricing", pricing_room_path, class: "sidebar-link active" %>
<% if !#room.price.blank? %>
<span class="pull-right text-babu"><i class="fa fa-check"></i></span>
<% end %>
</li>
<li class="sidebar-item">
<%= link_to "Description", description_room_path, class: "sidebar-link active" %>
<% if !#room.listing_nam.blank? %>
<span class="pull-right text-babu"><i class="fa fa-check"></i></span>
<% end %>
</li>
<li class="sidebar-item">
<%= link_to "Photos", photo_upload_room_path, class: "sidebar-link active" %>
<% if !#room.photos.blank? %>
<span id="photo_check" class="pull-right text-babu"><i class="fa fa-check"></i></span>
<% end %>
</li>
<li class="sidebar-item">
<%= link_to "Amenities", amenities_room_path, class: "sidebar-link active" %>
<span class="pull-right text-babu"><i class="fa fa-check"></i></span>
</li>
<li class="sidebar-item">
<%= link_to "Location", location_room_path, class: "sidebar-link active" %>
<% if !#room.address.blank? %>
<span class="pull-right text-babu"><i class="fa fa-check"></i></span>
<% end %>
</li>
</ul>
<hr/>

Answer 1

You can't call .count on a nil. #photos must be instantiated first. You controller doesn't appear to instantiate #photos at all. I can't see where else in your code you're calling #photos but where it's getting called, the instance variable has not yet be defined. Your controller create method only shows it happens if params[:images] is present, if otherwise it will be nil.
Try to instantiate #photos outside the if block.
def create
#room = Room.find(params[:room_id])
#photos = #room.photos
if params[:images]
params[:images].each do |img|
#room.photos.create(image: img)
end
redirect_back(fallback_location:request.referer, notice: "Saved...")
end
end
UPDATE: Ruby 2.3+ you can use safe navigation with & :
def create
#room = Room.find(params[:room_id])
params[:images]&.each{|img| #room.photos.create(image: img)}
redirect_back(fallback_location: request.referer, notice: "Saved...")
end
Or why bother using separate #photos in view when you should be able to just call #room.photos in it's place.
Instead of calling .count as your conditional in the view, use #room.photos.present?
One more suggestion is to prefer to use positive if case. so change
if !#room.photos.blank?
# better to use this below
if #room.photos.present?
Also, one would assume before a create action, you need a new action in your controller where one would expect #photos to be defined if it really needs be isolated from #room.photos. This is standard MVC in rails, but not sure if you've posted all of your code correctly so I'm guessing here.

Answer 2

The people above have already given great explanations as to why you can't call a method on a nil class. In addition, maybe the following code will help in your situation:
<% if !#photos.nil? && #photos.count > 0 %>

Answer 3

<% if #photos.count > 0 %>
If this fails with an error 'undefined method for nil class', then it means #photos is nil, and you therefore can't perform any methods on it. Where are you calling it? You've not included it in your code.
When you click on the link, look at your server logs and it will tell you which controller action you are hitting. Whichever action you're hitting, is where you'll need to define #photos.
If it is photos#create (the controller action you listed above) then it means that #room.photos is nil. That's unlikely, as it would almost certainly return an empty active record relation if anything, so your problem is not defining #photos in the controller and action you're using at that time.