Rubyscape

How are they different? http://blog.krishnaswamy.in/blog/2012/02/04/ruby-inject-vs-each-with-object/

As described in http://blog.jayfields.com/2008/03/ruby-inject.html

Inject can be really useful to do the following

Summing out numbers without using a temp variable

Building a hash out of double arrays

var_a, var_b = [1,2]

=> var_a = 1

While you like in the Ruby Rails world, i am sure bundler is one of the tool most frequently used at your disposal.

Here are a few things you can do with the bundle command :-

bundle show <gem name> # shows you the path to the gem

update_attribute without the 's' actually skips validation! http://api.rubyonrails.org/classes/ActiveRecord/Persistence.html#method-i-update_attribute

What is Rack? Rack is an interface to allow the web server to interact with a web app.

What is Rack Middleware? Rack Middleware acts as a filter that intercepts a request coming to the web server before hitting the application. It can also filter responses coming out from the application.

The point is,

Think of it this way, there is a "config.ru" file in your Rails application. The Rack server will look for that file, which is essentially a Rackup file. So we know that Rails is a Rack application.

You can find out how Rails uses Rack by calling

rake middleware

Now you can see all the middlewares that were installed and used in this application.

When a request comes in, it will hit each and every one of these middlewares and ends at the bottom which is the application.

It is possible to write your own middleware as stated in http://railscasts.com/episodes/150-rails-metal-revised

To add a written middleware into the queue

config.middleware.insert_before <any middleware>, <your middleware>

config.middleware.insert_before <number>, <your middleware>

config.middleware.use <your middleware>

Useful Resources

It has been stressed that applying conditions or sorting on an Eager Loading Query may have unintended consequences.

May refer to the following:-

http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#label-Eager+loading+of+associations

http://snaprails.tumblr.com/post/234198162/eager-loading

http://stackoverflow.com/questions/9642900/eager-loading-the-right-way-to-do-things

http://guides.rubyonrails.org/active_record_querying.html#specifying-conditions-on-eager-loaded-associations

That is if you have the following,

posts.includes(:comments, :commenters).where("comments.created_at > ?", 1.week.ago)

You probably expect to get all the posts with comments and commenters eager loaded, BUT the comments should be filtered to be all later than 1 week ago.

However, you will find that the result you would get is - all posts with comments that were created more than 1.week.ago, the other posts will not be returned in the result.

Solution?

You can specify an association with condition in the Post model like so,

1. http://railscasts.com/episodes/245-new-gem-with-bundler

2. http://railscasts.com/episodes/301-extracting-a-ruby-gem : In this episode Ryan described a few key components needed to get a gem up and running. They involved turning a snippet of code from your existing Rails app, package them into a gem, implementing adding model feature, and some great gems to help in model testing within the gem.

3. http://railscasts.com/episodes/303-publishing-a-gem : Basically covers housekeeping things to do before releasing your gem to Rubygems. Like making sure that the gem is well described, versioning, and continuous testing on Travis CI

4. http://guides.rubygems.org/make-your-own-gem/ : Wonderful guide on how to get the most basic gem up and running.

A few things i have noted when you are developing your own Gem :-

While it is important to test your gem, you want to make sure that you set them up correctly. Create a test directory, with some test helper, and a bunch of test files. You can use rspec or minitest. It would also be convenient to add a Rake task to run the test, include adding the load path for the test and lib directories. That shall make your test work.

The correct load path also allows you to use require around the ruby files instead of relying on require_relative or using absolute path.