Rails 4: assets on Heroku - ruby-on-rails

Question

I have deployed my app to heroku, but some assets are not loading, e.g.:
GET https://myapp.herokuapp.com/javascripts/s3_direct_upload.js - 404
GET https://myapp.herokuapp.com/stylesheets/s3_direct_upload_progress_bars.css - 404
the problem is in precompile, I have to add every file manually to assets.rb
but I don't really want to do it, because there are many of them
in my assets.rb I tried:
Rails.application.config.assets.precompile << Proc.new { |path|
if path =~ /\.(css|js)\z/
full_path = Rails.application.assets.resolve(path).to_path
app_assets_path = Rails.root.join('app', 'assets').to_path
if full_path.starts_with? app_assets_path
puts "including asset: " + full_path
true
else
puts "excluding asset: " + full_path
false
end
else
false
end
}
and:
Rails.application.config.assets.precompile = false
but it's not working
I've added to application.rb
config.serve_static_files = true
also, //=require from my precompilled assets are not included into header
everything works good in dev environment on my laptop
what do I need to change to make it work in production?
Update
I use helper, to include some js and css files in views:
def javascript(*files)
content_for(:foot) { javascript_include_tag(*files) }
end
and in my view I have:
<% stylesheet 's3_direct_upload_progress_bars' %>
<% javascript 's3_direct_upload', 'init.script.js' %>
assets from gem s3_direct_upload are not loading
init.script.js is located in assets/javascripts, so it is loading as it should be
another problem, in my application.js I have:
//= require jquery
//= require jquery.slicknav.min.js
$(function ()
{
$('#menu').slicknav();
});
after assets:precompile it looks okay, but in console I have error:
$(...).slicknav is not a function
so it was compiled wrong? everything works good in development environment
Update 2
Ignore the second problem, I found second require for jquery, it caused this error
but I still can't include assets from gem without precompile,
can I somehow disable this behavior? I just want include some assets for specific actions without headache

Answer 1

By default Rails 4 will not serve your assets. To enable this functionality you need to go into config/application.rb and add this line:
config.serve_static_assets = true
Alternatively you can achieve the same result by including the rails_12factor gem in your Gemfile:
gem 'rails_12factor', group: :production
This gem will configure your application to serve static assets so that you do not need to do this manually in a config file.
Hope this will work for you.