Ruby on Rails cannot load concern module

Question

I have initialized a module in the folder "concerns" located in: appname/app/models/concerns

called current_cart.rb

appname/app/models/concerns/current_cart.rb

module CurrentCart
  extend ActiveSupport::Concern

private

    def set_cart
        @cart = Cart.find(session[:cart_id])
    rescue ActiveRecord::RecordNotFound
        @cart = Cart.create
        session[:cart_id] = @cart.id
    end
end

i'm including this in my controller line_item_controllers:

appname/app/controllers/line_items_controller.rb

class LineItemsController < ApplicationController
  include CurrentCart

but it produces this error when i try to execute on my browser:

uninitialized constant LineItemsController::CurrentCart

app/controllers/line_items_controller.rb:2:in `<class:LineItemsController>'
app/controllers/line_items_controller.rb:1:in `<top (required)>'

Is app/models/concerns in your load_paths?

BroiSatse
– BroiSatse

2014-09-30 09:59:20 +00:00
Commented Sep 30, 2014 at 9:59 — BroiSatse
– BroiSatse, Commented Sep 30, 2014 at 9:59
Which rails version you are using?

Ernest
– Ernest

2014-09-30 10:01:41 +00:00
Commented Sep 30, 2014 at 10:01 — Ernest
– Ernest, Commented Sep 30, 2014 at 10:01
i'm using a version of rails 4.0

giovaZ
– giovaZ

2014-09-30 10:14:51 +00:00
Commented Sep 30, 2014 at 10:14 — giovaZ
– giovaZ, Commented Sep 30, 2014 at 10:14

Ernest · Accepted Answer · 2014-09-30 10:15:29Z

3

Nothing seems to be wrong here, if we are talking about Rails 4 - it should work out of the box.

However, what you are doing is a slight misuse of what concerns are for. And you are defining models/concerns, where you should put this one in controllers/concerns (for readability's sake).

For this case, controller filters are more suitable.

class LineItemsController < ApplicationController
  before_action :set_cart

  private

  def set_cart
    @cart = Cart.find(session[:cart_id])
  rescue ActiveRecord::RecordNotFound
    @cart = Cart.create
    session[:cart_id] = @cart.id
  end  
end

edited Sep 30, 2014 at 10:15

answered Sep 30, 2014 at 10:03

Ernest

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Comments

Steve · Accepted Answer · 2014-10-14 00:55:50Z

2

Based on the code, I'm assuming you are following along with the book, "Agile Web Development with Rails."

I would recommend just moving your code from:

appname/app/models/concerns/current_cart.rb

to:

appname/app/controllers/concerns/current_cart.rb

This would allow you to most easily follow the example in the book.

answered Oct 14, 2014 at 0:55

Steve

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Comments

bartoindahouse · Accepted Answer · 2016-04-03 18:37:04Z

1

Was having the same problem. For me it was a simple bug. It couldn't read LineItemsController::CurrentCart because when I created current_cart.rb it was saved with an aditional white space at the end (after .rb), .eg current_cart.rb(space)

So after deleting the white extra space it all worked out well.

answered Apr 3, 2016 at 18:37

bartoindahouse

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1 Comment

user1547410 Over a year ago

Mine was similar, I forgot to put .rb at the end of the filename, seeing this helped me find that when I was looking for a space at the end so kudos

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