Ruby on Rails - nil:NilClass 错误的未定义方法`each'

Question

I've gone over the API for my specific error and the answers provided are not able to solve my issue.

I'm just experimenting with a "find nearest location" code obtained online, and my issue is that when I am implementing this code to a project, I am obtaining the "undefined method `each' for nil:NilClass error".

I understand this error would be due to, when calling an @something, it isn't defined. So, this is the code and files I'm working with:

locations.rb

class Nearby_Location < ActiveRecord::Base
  geocoded_by :full_address
  after_validation :geocode, :if => :address_changed?

  def full_address
   [address, city, postcode].compact.join(',')
  end
end

locations_controller.rb

class Locations < ApplicationController
  def index
    @locations = Locations.all
    if params[:search].present?
      @locations = Locations.near(params[:search], 10, :order => :distance)
    else
      @locations = Locations.all.order("created_at DESC")
    end
  end

  def new
    @locations = Locations.new
  end

  def create
    @locations = Locations.new(location_params)
    if @locations.save
      flash[:success] = 'Place added!'
      redirect_to root_path
    else
      render 'new'
    end
  end

  def location_params
    params.require(:location).permit(:company_name, :address, :city,
                                    :postcode, :latitude, :longitude)
  end

  def show
    render :layout => nil
    @locations = Locations.find(params[:id])
  end

end

page.html.erb

<div class="container">
  <div class="starter-template">
    <h3>Find places near your location</h3>
    <p class="lead">Enter your address or zip code</p>
    <p><%= form_tag locations_path, :method => :get do %>
      <%= text_field_tag :search, params[:search], placeholder: "e.g Statue of Liberty, New York" %>
      <%= submit_tag "Search Near", :name => nil %>
      <% end %>
    </p>
  </div>

  <% @locations.each do |locations| %>
 <%= link_to locations do %>
  <%= locations.name %>
 <% end %>
<% end %>

</div>
</div>

scheme.rb

  create_table "locations", force: :cascade do |t|
    t.string "address"
    t.float "latitude"
    t.float "longitude"
  end

I've modified with the code incorporating the answers of the other APIs but with no success. I feel it may be due to the def show portion of the code, but I'm not too sure.

Answer 1

You did not specify which controller action you hit this error in, however based off your code I guess it is from the show method. The issue is probably that you are trying to not render the layout, however you are doing this before setting the @locations variable. Therefore, Rails is going into rendering before the instance variable has been created. To fix, you should move render :layout => nil line to the end of your method, after the instance variables have been created, eg:

def show
  @locations = Locations.find(params[:id])
  render :layout => nil
end

However, I think you may not be fully understanding the flow of events happening here based off the names of your files. By default, at the end of a controller action, Rails will attempt to render a file by looking for a file name matching the controller action from within a views folder matching the name of the controller. For example:

app/controllers/books_controller.rb :

class BooksController < ApplicationController
  def index
    # Will automatically render `app/views/books/index.html.erb`
  end

  def show
    render :other_show_page # Will look for a file `app/views/books/other_show_page.html.erb` rather than `app/views/books/show.html.erb` because it was explicitly specified
  end
end

In your case, you have a file called page.html.erb but you do not have a controller action ( def page; end ) nor are any of your other actions specifically rendering a file called page . As such, Rails would not be able to find your page.html.erb file anyway. I assume you do have a show.html.erb file or else you would be getting a different error, however if you are trying to render the HTML from within your page.html.erb file, it will not happen from within your show method unless you specifically render that file.

A few other notes...

• Models should typically have names in the singular, rather than plural. You appear to be using Locations as your model name, rather than Location .
• Your instance variable in your show method @locations , though you are using the find ActiveRecord query. This query returns a single object, rather than a collection proxy of many objects. As such, your @locations variable naming is slightly misleading, and may be better as @location .
• If you are trying to render the page.html.erb file when you hit the show method, unless there is some specific reason you are doing this it is unnecessary and bad practice. You should just include the code in a show.html.erb file and let Rails automatically render it rather than creating a custom file that you are rendering specifically. Rails is convention over configuration, so try to learn the conventions and follow them until you have a good reason to break away.