Nowadays it is fairly easy to intercept and modify mails globally before they are sent. All you have to do is register an interceptor class which responds to .delivering_email(message). This card will show you two common use cases.

Subject prefix:

Usually you want to prefix the subject line of emails with the current environment (except production) so you can differentiate between production mails and mails from other environments. Of course a...

Rails supports time zones, but there are several pitfalls. Most importantly because Time.now and Time.current are completely different things and code from gems might use one or the other.

Especially configuring an application that cares only about one time zone is a bit tricky.

The following was tested on Rails 5.1 but should apply to Rails 4.2 as well.

Using only local time

Your life will be easier if your application does not need to support time zones. Disable them like this:

config.time_zone = 'Berlin' # Your local ...

You can use gem list to list all gems available from a remote gem server:

gem list -r --clear-sources -s 'https://user:password@gemserver.tld/'

This is useful to debug cases where Bundler complains of a gem existing in more than one gem source.

Ruby's standard library is in the process of being gemified. It will soon - Ruby 2.5 - consist of RubyGems, which can be updated independently from Ruby.

This might mean smoother Ruby upgrades in the future. If breaking API changes happen in standard gems, we can update these before upgrading Ruby.

Middleman is a static page generator that brings many of the goodies that Rails developers are used to.

Out of the box, Middleman brings Haml, Sass, helpers etc. However, it can be configured to do even better. This card is a list of improvement hints for a Rails developer.

Gemfile

Remove tzinfo-data and wdm unless you're on Windows. Add these gems:

gem 'middleman-livereload'
gem 'middleman-sprockets' # Asset pipeline!

gem 'bootstrap-sass' # If you want to use Bootstrap

gem 'byebug'

gem 'capistrano'
gem 'capistrano-mid...

In case you want to require a gem, that is not in the Gemfile of you bundle and therefore not in your loadpath, you need to add the path manually and require the gem afterwards.

Expected error

Requiring a gem, that is not in the Gemfile or .gemspec, will cause an LoadError exception:

require 'example_gem' => LoadError: cannot load such file -- example_gem

Adding a gem to the loadpath temporary

1. You need to install the gem

gem install 'example_gem'

2. Then you need to require the path where the gem was install...

The parallel-gem is quite easy to use and can speed up rendering time if you want to render the same partial multiple times (e.g. for rendering long lists of things).

Parallel supports execution using forked processes (the default), threads (mind the GVL) and Ractors (some limitations for data sharing).

If your parallelized code talks to the database, you should [ensure not to leak database connections](https://makandracards.com/makandra/45360-using-activerecord-with-threads-will-leak-database-connect...

For the initial setup or changes in the sentry reporting it might be useful to enabled reporting of sentry in development. Don't commit these changes and prefer to report to the staging environment. As other developers might be confused of these errors try to given them a proper message and delete them afterwards.

1. Add config.raven_dsn = 'your-dns' in config/environments/development.rb.
2. Add development to existing environments in the Raven.configure block: config.environments = ['development', 'staging', 'production'].
3. ...

Barby is a great Ruby gem to generate barcodes of all different sorts.

It includes support for QR codes via rQRCode; if you need to render only QR codes, you may want to use that directly.

Example usage

Generating a barcode is simple:

>> Barby::Code128.new('Hello Universe').to_png
=> "\x89PNG\r\n\u001A..."

Configuration

Barby supports several barcode types and you must require all necessary files explicitly.

For the example a...

Error:

/home/.../ruby/gems/2.1.0/gems/bundler-1.14.3/lib/bundler/rubygems_ext.rb:45:in `full_gem_path': uninitialized constant Bundler::Plugin::API::Source (NameError)

Solution: Upgrade Rubygems beyond 2.6.9.

Adding a gem means you take over the liability towards the external code.

Checklist

Based on "To gem, or not to gem":

• Gem is really needed (prefer writing your own code for simple requirements without many edge cases)
• Gem is tested well (coverage and quality)
• Gem has a good code quality
• Gem's licence fits to the project requirement
• Try to avoid gems that do much more than your requireme...

We generally use multiple application servers (at least two) and you have to search on all of them if you don't know which one handled the request you are looking for.

Rails application logs usually live in /var/www/<project-environment-name>/shared/log.
Web server logs usually live in /var/www/<project-environment-name>/log.

Searching through single logs with grep / zgrep

You can use grep in this directory to only search the latest logs or zgrep to also search older (already zipped) logs. zgrep is used just like grep ...

Why

We have projects that have been developed using many different versions of Ruby. Since we do not want to constantly update every old project, we need to have many Ruby versions installed on our development machines.

Rbenv does that for us.

How it works

Rbenv installs ruby version and ruby gems to ~/.rbenv/versions/VERSION_NUMBER/.... This way many different Rubies can be installed at once.

When you run ruby or gem or bundler or any other Ruby binary

• rbenv looks for a file...

On application servers, gems are usually bundled into the project directory, at a location shared across deployments.

This is usually shared/bundle inside your project's root directory, e.g. /var/www/your-project/shared/bundle/.
If you can't find that, take a look at current/.bundle/config and look for BUNDLE_PATH.

When you are changing the version of RubyGems or Bundler on a system where gems are installed this way, you must wipe that bundle directory in addition to the user and system gems or gems that are already ins...

Error

deadlock 0x7f8a4160a360: sleep:- (main) - /home/me/.rbenv/versions/1.8.7-p375/lib/ruby/gems/1.8/gems/bundler-1.14.3/lib/bundler/worker.rb:43
deadlock 0x7f8a38c03b08: sleep:-  - /home/me/.rbenv/versions/1.8.7-p375/lib/ruby/gems/1.8/gems/bundler-1.14.3/lib/bundler/worker.rb:56
*** longjmp causes uninitialized stack frame ***: /home/me/.rbenv/versions/1.8.7-p375/bin/ruby terminated

... followed by a backtrace, memory map and more.

Fix

The culprit seems to be Bundler 1.14 when used with Ruby 1.8.7. [Downgrade to the maximu...

This error message may occur when rspec gets loaded by rake, e.g. when you migrate the test database.

NoMethodError: undefined method 'last_comment' for #<Rake::Application:0x0055a617d37ad0>

Rake 11 removes a method that rspec-core < 3.4.4 depends on. To fix, lock Rake to < 11 in your Gemfile:

  gem 'rake', '< 11', # Removes a method that rspec-core < 3.4 depends on

There are some inconvenient Gem dependencies. Resolve them by adding/modifying these lines in your Gemfile:

  gem 'guard-livereload', '>= 2.5.2', require: false # Fixes a security issue
  gem 'listen', '< 3.1' # 3.1 requires Ruby 2.2.5

It is not possible to install guard-livereload 2.5.2 on Ruby 1.8.7 because it depends on guard 2.8, which requires Ruby 1.9.

The rack-contrib gem brings a JSONP middleware that just works™. Whenever a JSON request has a callback parameter, it will wrap the application's JSON response appropriately.

The project is a bit dated, but the JSONP middleware is ok.

So you're getting an error like this:

undefined method `activate_bin_path' for Gem:Module (NoMethodError)

Here is what happened:

• You installed a recent version of Rubygems
• You installed some gems that install a binary (like bundle, rake or rails) with code that only works with modern Rubygems versions
• You downgraded Rubygems to an older versions, which doesn't change any binaries
• When calling binaries with the old Rubygems version, it cannot process the line Gem.activate_pin_path(...) that was written out by th...

TL;DR: Update the 'net-ssh' gem by adding to your Gemfile:

gem 'net-ssh', '=2.9.1'

Now run bundle update net-ssh. It has no dependencies so it shouldn't update other gems.

If you're using Ruby 1.8.7 and want to update net-ssh to a version > 2.9.1 you also need to add this to your gemfile:

gem 'backports', :require => false

... and in your deploy.rb add this:

require 'backports/1.9.2/array/select' 

Background

You propably have an older version of Capistrano and thereby an older version of `n...

So you're getting this failure when running bundle install on an older project:

Your Gemfile.lock is corrupt. The following gems are missing from the DEPENDENCIES section: 'archive-tar-minitar' 'hoe' 'rcov'

This happens when you are using a new version of Bundler with a project that was bundled with a very old version of Bundler. For reasons unknown, the Bundler dependency API returns different dependencies for some gems (like ruby-debug or rainpress) than the dependencies found in the downloaded gemspecs. While old versi...