Using Mongoid 3 (MongoHQ or MongoLab) on Heroku

Here's what you need to get Mongoid working on Heroku, if you're getting errors like:
NoMethodError (undefined method `[]' for nil:NilClass)

Make sure the following is in your gem file (reference).

source 'http://rubygems.org' 

ruby '1.9.3'
gem  'rails', '3.2.3'

If you get an error like undefined method `ruby' run the following:

gem install bundler --pre

A lot of places have outdate documentation for configuring your mongoid.yml file which may result in the following error:
No database provided for session configuration: :default

Your mongoid.yml file should look like the following.

production:
  sessions:
    default:
      uri: <%= ENV['MONGOHQ_URL'] %>
      options:
        skip_version_check: true
        safe: true

The ENV variable above is for MongoHQ. For MongoLab use ENV['MONGOLAB_URI'] 


Big thanks to the guys in this StackOverflow thread for helping me put all this together!

Ruby Cheat Sheet for .NET Developers

....or anybody who sucks at OSX/Linux.

I've been learning Ruby on Rails over the last couple of months and when you've been programming on Windows with Visual Studio for as many years as I have it's a major learning curve to switch to programming Ruby on OSX or Linux. So I've created a cheat sheet to help me with all the little details I routinely have to look up.

Ruby on Rails Command Line

Preview Site:

rails server

Preview Site as Production:

rails s -e production

Test DB and be able to rollback changes:

rails console --sandbox

Reset DB:

rake db:reset

Modify DB for real:

rails console

View ActiveRecord Raw SQL:

tail -f log/development.log

Migrate Development DB

rake db:migrate (DEV)

Migrate Test DB

rake db:test:prepare

Migrate Production DB

rake db:migrate RAILS_ENV=production

Create a New DB Migration:

rails generate migration [MIGRATION NAME] 

rails generate migration add_email_uniqueness_index

View Routes:

rake routes

Start Autotest:

autotest

Ruby on Rails 

Output debug info in Model:

logger.debug @user.attributes.inspect

Add Debug info to Layout:

<%= debug(params) if Rails.env.development? %>

Routes:

NAMED ROUTE            PATH
users_path             /users
user_path(@user)       /users/1
new_user_path          /users/new
edit_user_path(@user)  /users/1/edit
users_url              http://localhost:3000/users
user_url(@user)        http://localhost:3000/users/1
new_user_url           http://localhost:3000/users/new
edit_user_url(@user)   http://localhost:3000/users/1/edit

Routing Info:

http://www.engineyard.com/blog/2010/the-lowdown-on-routes-in-rails-3/

RESTFUL Routes:

GET      /photos           index     display a list of all photos
GET      /photos/new       new       return an HTML form for creating a new photo
POST     /photos           create    create a new photo
GET      /photos/:id       show      display a specific photo
GET      /photos/:id/edit  edit      return an HTML form for editing a photo
PUT      /photos/:id       update    update a specific photo
DELETE   /photos/:id       destroy   delete a specific photo

Ruby Syntax

Assign if variable is undefined:

||=  

@current_user ||= user_from_remember_token

Variable Scope:

$            A global variable
@            An instance variable
[a-z] or _   A local variable
[A-Z]        A constant
@@           A class variable

http://www.techotopia.com/index.php/Ruby_Variable_Scope 

RVM

Upgrade to the latest version of rvm

rvm update --head

Install a version of Ruby

rvm install 1.9.2

Working with gemsets

rvm info                        # show the current environment
rvm 1.8.7                       # use the ruby to manage gemsets for
rvm gemset create project_name  # create a gemset
rvm gemset use project_name     # use a gemset in this ruby
rvm gemset list                 # list gemsets in this ruby
rvm gemset delete project_name  # delete a gemset
rvm 1.9.1@other_project_name    # use another ruby and gemset

Default for Project:

echo "rvm 1.9.1@MyProject" > ~/projects/MyProject/.rvmrc

Ruby Gems

Add gem to Gemfile

Run:

bundle install

or 

bundle update

or (for self contained)

bundle pack

Unix Command Line

Extract tar.gz:

tar -zxvf yourfile.tar.gz

Find a file:

find . -name "controller.rb" 

http://helpdesk.ua.edu/unix/tipsheet/tipv1n10.html

Delete Folder:

rm -rf

Add JPG File Extension to Multiple files:

for f in *; do mv "$f" "$f.jpg"; done

Git

Remove file from repo:

git rm --cached

GitHub

Checkout:

git clone git://github.com/crdeutsch/MVC3-Boilerplate.git

Publish:

git push origin master

Git Flow

Enable Git Flow

git flow init

Start a Feature

git flow feature start myfeature

Finish a Feature

git flow feature finish myfeature

Heroku

Create App:

heroku create

Publish:

git push heroku master

Migrate DB:

heroku rake db:migrate

View Logs:

heroku console
File.open('log/production.log', 'r').each_line { |line| puts line }

Compass

Compile CSS:

compass compile

Watch project for changes and compile whenever it does:

compass watch

StaticMatic

New site:

staticmatic setup my_site

Preview:

staticmatic preview my_site

Build:

staticmatic build my_site

OSX

Screen Capture:

Full Screen:

Hold down Apple key ⌘ + Shift + 3 and release all

Portion of your screen:

Hold down Apple key ⌘ + Shift + 4 and release all key

Application window:

Hold down Apple key ⌘ + Shift + 4 and release all key
Now, You will see the mouse cursor will change to +
Press the space bar once

This list is far from comprehensive, but it's pretty much everything I've had to google at least once to figure out and I plan to keep adding to it as I progress.

If you have some nuggets to share add them to the comments.

If lots of people want to contribute we should probably move this to a different format (Wiki, Markdown?) but until then I'll keep maintaining it here.