This article is part of our Upgrade Rails series. To see more of them, click here.

This article will cover the most important aspects that you need to know to get your Ruby on Rails application from version 5.1 to 5.2.

Transcript:

Hello and welcome to the first OmbuCast by OmbuLabs. In this screencast we’ll be taking a look at the derailed_benchmarks gem, and how you can use it to benchmark your Rails application and find, and hopefully fix bottlenecks in your code.

This article is part of our Upgrade Rails series. To see more of them, click here.

This article will cover the most important aspects that you need to know to get your Ruby on Rails application from version 5.0 to 5.1.

This article is part of our Upgrade Rails series. To see more of them, click here.

This article will cover the most important aspects that you need to know to get your Ruby on Rails application from version 4.2 to 5.0.

This article takes a look at some of the changes to the ActiveRecord::Dirty module between Rails 5.1 and 5.2.

If you’re running Rails 5.1, you may have already seen some of the deprecation warnings related to the API changes contained in it. Most of them are behavior changes, and there are some new additions as well.

To better understand these modifications, we’ll take a look at sample projects in Rails 5.1 and Rails 5.2.

This article is part of our Upgrade Rails series. To see more of them, click here.

This article will cover the most important aspects that you need to know to get your Ruby on Rails application from version 4.1 to 4.2.

This article is part of our Upgrade Rails series. To see more of them, click here.

This article will cover the most important aspects that you need to know to get your Ruby on Rails application from version 4.0 to 4.1.

This article is part of our Upgrade Rails series. To see more of them, check our article title The Rails Upgrade Series.

A previous post covered some general tips to take into account for this migration. This article will try to go a bit more in depth. We will first go from 3.2 to 4.0, then to 4.1 and finally to 4.2. Depending on the complexity of your app, a Rails upgrade can take anywhere from one week for a single developer, to a few months for two developers.

When working on a Rails project, you may have seen present? calls on ActiveRecord relationships. This might feel natural, mostly because present? exists on all objects via ActiveSupport, so you expect the relationship to respond to it, but it’s actually not a very good idea. If all we want to do is check if the scope returns any results from the database, there are better ways than using present?.

A few weeks ago, I noticed weird output in the RSpec test suite (~4000 tests) for a Rails application:

.............................................................................................unknown OID 353414: failed to recognize type of '<field>'. It will be treated as String  ...........................................................................................................................................

This Rails app uses a PostgreSQL database. After some Googling, it turns out that this is a warning from PostgreSQL. When the database doesn’t recognize the type to use for a column, it casts to string by default.

When writing tests for services, you may sometimes want to use mock objects instead of real objects. In case you’re using ActiveRecord and real objects, your tests may hit the database and slow down your suite. The latest release of the rspec-mocks library bundled with RSpec 3 includes at least three different ways to implement a mock object.

Let’s discuss some of the differences between a spy, a double and an instance_double. First, the spy:

[1] pry(main)> require 'rspec/mocks/standalone'
=> true
[2] pry(main)> user_spy = spy(User)
=> #<Double User>
[3] pry(main)> spy.whatever_method
=> #<Double (anonymous)>

There are already quite a few guides in the wild to help with the upgrade of Rails 3.2 to Rails 4.0.

The official Rails guide for upgrading from Rails 3.2 to 4.0 is very thorough. With the recent release of Rails 5.0, apps currently in production running Rails 3.2 should probably be updated to any stable Rails 4 release as soon as possible.

There is even an e-book about upgrading from Rails 3 to 4, which serves as a useful guide to make this upgrade easier, and also helps understand the advantages & disadvantages of this new (soon to be old) version.

However, if you’re using any non-standard gems, you’re mostly on your own. Some gems stopped being maintained before Rails 4 was released, as was the case with CanCan, a well known authorization library. After many open pull requests were left unmerged, CanCanCan was released. It is a community driven effort to have a semi-official fork of CanCan. It serves as a drop-in replacement for people who want to use CanCan after upgrading to Rails 4.