Failed to load files from gems installled with rails 4

Question

I'm developing an webapplication with rails 4 and spine js as the frontend mvc framework. With gem 'spine-rails' installed, I ran the command

rails g spine:new

And in the app folder generated, the index.js.coffee file load some 3rd party assets.

#= require json2
#= require jquery
#= require spine
#= require spine/manager
#= require spine/ajax
#= require spine/route

#= require_tree ./lib
#= require_self
#= require_tree ./models
#= require_tree ./controllers
#= require_tree ./views

class Frontend extends Spine.Controller
  constructor: ->
    super

    # Initialize controllers:
    #  @append(@items = new Frontend.Items)
    #  ...

    Spine.Route.setup()    

window.Frontend = Frontend

when running the server, here comes an error that

Sprockets::FileNotFound at /
couldn't find file 'json2' (in /Users/edward/git/beta-cafe/app/assets/javascripts/frontend/index.js.coffee:1)

It seems that there js files like json2, spine, spine/ajax, are loaded in the gem folder.But Rails fails to load them.

Any solutions? :)

Answer 1

Add gem 'json2-rails' to your gemfile.

This solved the same issue for me. It shouldn't be necessary, though, because the spine-rails has that gem as a dependency.

Edit

After posting this answer, I confirmed my answer when I happened to look at the spine-rails github repo while working on another project. It says:

In your Gemfile, add the following lines:

gem "json2-rails"

gem "spine-rails"

So you must include the json2-rails gem in your gemfile.