Rails 4 + bootstrap set up assets

Question

I am trying to setup bootstrap on Rails4 using bootstrap-sass and I am getting this famous error:

Sprockets::FileNotFound - couldn't find file 'bootstrap'
  (in app/assets/javascripts/application.js:16):

I have tried following:

1. twitter/bootstrap in application.js
2. gem 'bootstrap-sass', '~> 3.1.0' is outside group assets
3. Also tried bunch of other things on internet

I have spend lot of time taking different suggestions from other posts. How do I systematically debug this , how to setup bootstrap-sass ?

p.s: Also been trying to get twitter-bootstrap-rails working with no luck.

Here are some files

application.js

//= require jquery
//= require jquery_ujs
//= require js-routes
//= require bootstrap
//= require_tree .
//= require bootstrap-slider

application.css.scss

 *= require jquery.ui.core
 *= require jquery.ui.theme
 *= require_self
 *= require bootstrap-slider
 *= require_tree .
 *= stub active_admin
*/

@import "bootstrap";

Gemfile

source 'https://rubygems.org'
ruby '2.0.0'
gem 'rails', '4.0.0'
gem 'sass-rails'
gem 'coffee-rails', git: 'git://github.com/rails/coffee-rails.git'
gem 'uglifier', '>= 1.0.3'
gem 'jquery-ui-rails'
gem 'font-awesome-sass'
gem 'less-rails'
gem 'therubyracer', :platform=>:ruby
#gem 'twitter-bootstrap-rails'
gem 'jquery-rails'
#gem 'jquery_mobile_rails'
gem 'js-routes'
gem 'cancan'
gem 'devise'
gem 'figaro'
gem 'haml-rails'
gem 'pg'
gem 'rolify'
gem 'sendgrid'
gem 'simple_form'
gem 'thin'
gem 'rake'

#To use db for storing cookies instead cookie-store
gem 'activerecord-session_store', github: 'rails/activerecord-session_store'

group :development do
  gem 'better_errors'
  #gem 'binding_of_caller', :platforms=>[:mri_19, :rbx]
  #Commenting out platforms part, because may be that's stopping this to be used on the dev machine'
  gem 'binding_of_caller'
  gem 'guard-bundler'
  gem 'guard-rails'
  gem 'guard-rspec'
  gem 'html2haml'
  gem 'quiet_assets'
  gem 'rb-fchange', :require=>false
  gem 'rb-fsevent', :require=>false
  gem 'rb-inotify', :require=>false

  # Required with Rails panel chrome extension. This Gem should come after better_errors gem
  gem 'meta_request'
end
group :development, :test do
  gem 'factory_girl_rails'
  gem 'rspec-rails'
  gem 'pry-byebug'
  gem 'pry-stack_explorer'
  gem 'pry-rails'
  gem 'pry-debugger'
end

group :test do
  gem 'capybara'
  gem 'database_cleaner'
  gem 'email_spec'
end

group :production do
  gem 'rails_12factor'
end

gem 'high_voltage'

#Linkedin Logins
gem "linkedin"
gem "omniauth"
gem "omniauth-linkedin"

gem "omniauth-facebook"

#postgres use hstore in active record
#gem 'activerecord-postgres-hstore'

gem 'state_machine'
gem "ruby-graphviz"


#payments
#gem 'stripe',:git => 'https://github.com/stripe/stripe-ruby'

#gem 'anjlab-bootstrap-rails', :require => 'bootstrap-rails', :github => 'anjlab/bootstrap-rails'

gem 'newrelic_rpm'

gem 'pgbackups-archive'

gem 'pg_search'

gem 'acts-as-taggable-on'

#gem 'activeadmin' , github: 'gregbell/active_admin'
gem "activeadmin", git: "https://github.com/gregbell/active_admin"

gem 'kaminari'
gem 'bootstrap-slider-rails'
gem 'bootstrap-sass', '~> 3.1.0'

Answer 1

Installing the Bootstrap Gem

1.) Add the Bootstrap Gem:

gem 'bootstrap-sass'

2.) Understand The Application.css File app/assets/stylesheets/application.css

Application.css takes all the other files in your /stylesheets directory and combines them for when you run your app.

3.) Create a New SCSS File (app/assets/stylesheets/bootstrap_and_customization.css.scss)

@import 'bootstrap';

4.) Require Bootstrap's JavaScript

...
//= require jquery
//= require jquery_ujs
//= require bootstrap <--
//= require turbolinks
//= require_tree .

5.) Rails Assets

group :production do
  gem 'rails_12factor'
end

6.) Bundle Install & Restart Server

Thats should be it !