tl;dr: Ruby's Bundler environment is passed on to system calls, which may not be what you may want as it changes gem and binary lookup. Use Bundler.with_original_env to restore the environment's state before Bundler was launched. Do this whenever you want to execute shell commands inside other bundles.

Example outline

Consider this setup:

my_project/Gemfile     # says: gem 'rails', '~> 3.0.0'
my_project/foo/Gemfile # says: gem 'rails', '~> 3.2.0'

And, just to confirm this, these are the installed Rails versions for each ...

There is no such thing as a "default order" of rows in database tables.

For instance, when you paginate a result set: When using LIMIT, it is important to use an ORDER BY clause that constrains the result rows into a unique order. Otherwise you will get an unpredictable subset of the query's rows. You might be asking for the tenth through twentieth rows, but tenth through twentieth in what ordering? The ordering is unknown, unless you specified ORDER BY.

In Rails, if you use Record.first or Record.last, it will default to orderin...

Slow test suites are a major pain point in projects, often due to RSpec and FactoryBot. Although minitest and fixtures are sometimes viewed as outdated, they can greatly improve test speed.

We adopted a project using minitest and fixtures, and while it required some initial refactoring and establishing good practices, the faster test suite was well worth it! Stick with me to explore how these tools might actually be a good practice.

So, why is this setup faster? Partially, it's because minitest is more lightweight than RSpec, which...

Remember How to skip Sprockets asset compile during Capistrano deployment and Automatically skipping asset compilation when assets have not changed? Turns out there is an even better way to speed up Capistrano deployments with asset compilation – and it's even simpler.

Adding the asset cache directory to symlinked directories

Popular asset managers for Rails are Sprockets and Webpacker. Both keep a cache of already compiled files that we're going to leverage for deployments now.

• Sprockets cache...

When using Rails to truncate strings, you may end up with strings that are still too long for their container or are not as long as they could be. You can get a prettier result using stylesheets.

The CSS property text-overflow: ellipsis has been around for quite a long time now but since Firefox did not support it for ages, you did not use it. Since Firefox 7 you can!

Note that this only works for single-line texts. If you want to truncate tests across multiple lines, use a JavaScript solution like...

In MySQL comparing zero to a string 0 = "any string" is always true!

So when you want to compare a string with a value of an integer column, you have to cast your integer value into a string like follows:

SELECT * from posts WHERE CAST(posts.comments_count AS CHAR) = '200' 

Of course this is usually not what you want to use for selecting your data as this might cause some expensive database operations. No indexes can be used and a full table scan will always be triggered.

If possible, cast the compared value in your application to...

View specs are a powerful tool to test several rendering paths by their cases instead of using a more costing feature spec. This is especially useful because they become quite convenient when used with Capybara::Node::Finders and Capybara::RSpecMatchers. This allows to wirte view unit specs as you can isolate specific part...

Capistrano is by default configured to exclude the gems of the groups development and test when deploying to the stages production and staging. Whenever you create custom groups in your Gemfile, make sure to exclude these, if they should not be deployed to the servers. The gems of these groups might not be loaded by rails, however, the deployment process will take longer as the gems will be downloaded and installed to the server.

e.g. to exclude the groups cucumber and deploy, add the following to `config/deploy/production.rb...

For our production servers we use Passenger as a Ruby application server. While it is possible to use Passenger for development as an Apache module, the installation process is not for the faint of heart.

Luckily Passenger also comes as a standalone binary which requires zero configuration.

You can Passenger Standalone as a replacement for Webrick or Thin if you'd like to:

• Use SSL certificates locally
• Get performance behavior that is closer to ...

Sometimes the need arises for SSL in local development. We have guides for different webservers, this one is for puma.

0. make sure mkcert is installed

1. create an SSL certificate for localhost with mkcert:

$ mkcert-v1.4.4-linux-amd64 localhost
Created a new local CA 💥
...

2. use the certificate in the Puma config config/puma.rb:

localhost_key = "#{File.join('localhos...

PostgreSQL, unlike MySQL, treats strings as case sensitive in all circumstances.

This includes

• comparison with = and LIKE
• collision detection in unique indexes

Usually this is fine, but some strings (like emails and usernames) should typically be treated as case insensitive.

There are a few workarounds available:

• use the citext extension (not recommended)
• use ILIKE instead of LIKE
• use Postgres' lower() function
• add an index on lower(email)

Probably th...

To reload a single-item association in Rails 5+, call #reload_<association>:

post.reload_author

In older Railses you can say

post.author(true)

A good tool to generate strong passwords and secrets is "apg". You can get it with

sudo apt-get install apg

To create a strong secret for sessions, hashed Paperclip paths, etc. say

apg -m128 -a1 -E\'\"

Arguments explained:

• The -m parameter defines the secret length
• -a1 makes apg choose from all 7-bit ASCII characters instead of just the alphabet
• -E\'\" excludes quote characters so you can easily paste the secret into a Ru...

The ActiveSupport::BroadcastLogger allows you to log to multiple sinks. You know this behavior from from the rails server command, that both logs to standard out and the log/development.log file.

Here is an example from the ActiveSupport::BroadcastLogger API:

stdout_logger = ActiveSupport::Logger.new(STDOUT)
file_logger = ActiveSupport::Logger.new("development.log")
broadcast = ActiveSupport::BroadcastLogger.new(stdout_logger, file_logger)

broadcast.i...

When you need to see the content of a page (i.e. not all the HTML but the relevant text body)

• you can do pp (html_content)
  • pp will format the html String human readable pretty printed
• where html_content can be replaced by one of the following commands:

Rails

body or response.body

Capybara:

• page.driver.html.content
• page.body

Webrat:

Nokogiri::HTML(response.body).content

The returned strings can be cleaned up by calling .gsub(/^\s*$/, '').squeeze("\n") on them.\
Although this may be useful for d...

When RSpecs runs the first feature spec, you may see log output like this:

Capybara starting Puma...
* Version 6.5.0, codename: Sky's Version
* Min threads: 0, max threads: 4
* Listening on http://127.0.0.1:39949

You can disable this behavior by tweaking Capybara's Puma server in your spec/support/capybara.rb:

Capybara.server = :puma, { Silent: true }

Note

You don't need to configure this if you're using system tests with modern versions of Rails. They do [exactly the same](https://github.com/rails/rails/blob/ma...

• To retrieve only unique combinations of the selected attributes: You can omit rows, where all selected columns are equal with the DISTINCT statement.
• To retrieve the group wise maximum of certain columns: You can keep only one record for each group with the DISTINCT ON statement, to omit equal rows within each specified group.

Use case

You have a query where you want only one record for a set of specifically ordered attributes.

How to use?

Let's say we look at the example how to query only the latest post for each user:
...

• Reading a URL via GET:

  curl http://example.com/
  

• Defining any HTTP method (like POST or PUT):

  curl http://example.com/users/1 -XPUT
  

• Sending data with a request:

  curl http://example.com/users -d"first_name=Bruce&last_name=Wayne"
  

  If you use -d and do not set an HTTP request method it automatically defaults to POST.

• Performing basic authentication:

  curl http://user:password@example.com/users/1
  

• All together now:

  curl http://user:password@example.com/users/1 -XPUT -d"screen_name=batman"
  

...

Rack::SteadyETag is a Rack middleware that generates the same default ETag for responses that only differ in CSRF tokens or CSP nonces.

By default Rails uses Rack::ETag to generate ETag headers by hashing the response body. In theory this would enable caching for multiple requests to the same resourc...

Note: For PostgreSQL you should use advisory locks. For MySQL we still recommend the solution in this card.

If you need to synchronize multiple rails processes, you need some shared resource that can be used as a mutex. One option is to simply use your existing (MySQL) database.

The attached code provides a database-based model level mutex for MySQL. You use it by simply calling

Lock.acquire('string to synchronize on') do
  # non-th...

Haml renders HTML with indentation reflecting the nesting level of elements. When it comes to white-space preserving content, this may become a problem: the content will be rendered including the HTML indentation.

Problematic: Preserved Indentation

.nest
  %span Reference
  %pre
    = content

<div class="nest">
    <span>Reference</span>
    <pre>
        Hello
        World
    </pre>
</div>

Better: Without Extra Indentation

Render with tilde ~ instead of equal...

We use foreman to start all necessary processes for an application, which are declared in a Procfile. This is very convenient, but the outputs of all processes get merged together. Especially while debugging you might not want other processes to flood your screen with their log messages.

The following setup allows you to start Terminator in a split view with the Rails server running in the left pane and all remaining processes running via foreman in the right pane. It was heavily inspired by [this card](https://makandracards.com/makandr...

When accepting GIF images, you will also accept animated GIFs. Resizing them can be a time-consuming task and will block a Rails worker until the image is processed.

Save yourself that trouble, and simply tell ImageMagick to drop any frames but the first one.

Add the following to your uploader class:

process :remove_animation

private

def remove_animation
  if content_type == 'image/gif'
    manipulate! { |image| image.collapse! }
  end
end

You may also define that process for specific versions only (e.g. only for thum...

This should be fixed in the latest LTS-branches of our mysql2 fork, 0.2.x-lts and 0.3.x-lts.

Use

gem 'mysql2', git: 'https://github.com/makandra/mysql2', branch: '0.2.x-lts' # for Rails 2.x
gem 'mysql2', git: 'https://github.com/makandra/mysql2', branch: '0.3.x-lts' # for Rails 3.x

in your Gemfile, and do a

bundle update mysql2

Background

mysql2 used to check that the client library used at runtime actually matches the one it was compiled against. However, at least on Ubunt...