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More Rails: Beyond Backend:

Some Gems for Rails

Some Gems for Rails

This guide lists a few valuable gems for your first Rails Project.

After reading this guide you will

  • understand how gems are installed
  • understand how bundler handles dependencies
  • be able to configure the gems you use
  • be able to deliberately chose version numbers for your gems
  • know a few intresting gems for your next rails project

1 Gems and Bundler

1.1 gems

Code reuse is a deciding factor for programmer productivity. In Ruby the unit of reuse is called a gem. rubygems is the package manager for ruby, it let's you install gems on your system.

A gem has a name (e.g. rake) and a version number (e.g. 10.4.2). It can be written in plain ruby or sometimes in ruby and c. Many gems depend on system libraries that need to be installed before the gem can be installed. For example the rmagick gem for image manipulation needs the library ImageMagick.

So most of the time installing a gem is as simple as

> gem install rails_best_practices
Successfully installed rails_best_practices-1.15.7
Parsing documentation for rails_best_practices-1.15.7
Installing ri documentation for rails_best_practices-1.15.7
Done installing documentation for rails_best_practices after 2 seconds
1 gem installed

But sometimes you have to do other installations first. On your development machine this might look like this:

# install node on a mac
> brew install nodejs
> gem install uglifier

Sometimes you need to set include paths when compiling the c-part of the gem, e.g.:

> gem install eventmachine 
... error messages ...
In file included from binder.cpp:20:
./project.h:116:10: fatal error: 'openssl/ssl.h' file not found
#include <openssl/ssl.h>
> brew install openssl
> gem install eventmachine -- --with-cppflags=-I/usr/local/opt/openssl/include

In production you probably have to deal with Linux, and you may not have the right permissions to install system libraries. A typical example would be:

$dev> ssh my.production.machine
$production> sudo apt-get install libmagick++-dev
$production> gem install rmagick
$production> gem install paperclip

Now that you have installed the gem once by hand you can be sure that it can also be reinstalled by bundler.

See also:

1.2 dependency hell

For a rails project you will be using a lot of gems. This will lead to two problems:

  1. dependency resolution: gem A depends on version 1.1 of gem C, while gem B wants at least version 1.5. You need to find the right version of every gem in your project that actually fits together
  2. different installation: when deploying to a production server, or even just when shareing code with other developers you need to make sure that the same constellation of gems and versions is used on every machine

1.3 bundler saves us


Bundler is the name of the tool that saves us from dependency hell. Bundler is itself a gem, so you install it with gem install bundler. Beware: the command you will be using called bundle, not bundler.

There is how it works: In every ruby project you write a Gemfile in which you define which gems and (to a certain degree) which versions you want. When you run bundle install bundler will:

  • read the Gemfile,
  • pick out compatible versions of all the gems (if possible),
  • install all these gems
  • write Gemfile.lock

The lock-file contains a complete list of all the gems necessary for your project, and their version numbers. These are now locked down, and will not change!

When deploying to a new development machine or the production server, you run bundle install and the exact same versions are now installed.

1.4 defining versions

In the Gemfile you can specify which versions should be used. But don't overdo it! Bundler does a good job picking versions, if you specify every version number by hand you are doing too much work.

Some examples of the different ways of specifying version number and source:

# Gemfile
source ''

ruby '2.3.1'

gem 'rails', '~> 5.0.0', '>='
gem 'sqlite3'
gem 'puma', '~> 3.0'

The arrow ~> will only allow an increase in the last (right most) number, so ~> 5.0.0 does allow but not 5.0.1 or 5.1. This is called a pessimistic version constraint, read more about it in the rubygem documentation.

1.5 gems and rails

The configuration for a gem is found in the initializer directory, for example for devise the configuration file would be config/initializers/devise.rb.

A gem may install new generators for rails, run rails generate to see a list of available generators.

A gem may install rake tasks, run rails -T to see a list.

2.1 File Upload

File Upload has been integrated into Rails 5 with ActiveStorage, there is no need to use carrierwave or or paperclip and more.

After file upload you might want to resize or crop your images automatically. This is traditionally done with the library ImageMagick:

  • gem rmagick image processing with image magick

You might also want to know how to use ImageMagick on the UNIX commandline:

  • command line tool convert to convert to different formats and
  • command line tool mogrify to resize, blur, crop, draw on, flip, join, ... an image and overwrite it.

2.2 Authentication

  • gem devise for login,
  • gem omniauth to integrate authentication methods.
  • gem cancancan if you need roles and permissions

You don't want the database keys to be visible in your URLs? Use Friendly IDs instead:

2.4 Parsing xml and html

(this is also used by capybara)

2.5 Let Users format their Texts

Letting users enter HTML is a dangerous idea - it's really hard to avoid the security problems. An alternative is to let them enter a simpler markup language, like Markdown. You store the markdown in your database, and convert it to HTML when displayed using a gem:

Or use the builtin editor (since rails 6):

2.6 Pagination

Do you need to displaying a lot of items? Use a pagination gem to go through them page by page:

2.7 Filter

You need to filter objects shown by the index action?

  • gem brita can be used in APIs and full rails apps

2.8 Ordered Lists

You need to search in more than just one attribute of your model? use a search gem:

  • gem ransack for building search fields
  • gem pg_search uses postgresql's fulltext search
  • gem searchkick uses elasticsearch with many more options for fulltext search, e.g. for misspellings
  • other gems in category rails_search of the ruby toolbox

2.10 Activity Stream

If you want to give users an overview of what happened recently you can use an activity stream, similar to what you see in facebook.

activity stream example

2.11 Admin Backend

Create a Backend for manipulating data with a few lines of code:

ActiveAdmin Screenshot

2.12 Sending Mail

To send mail from Rails use ActionMailer.

To see the generated mails in your web browser instead of sending them, use the gem letter_opener

To receive Mail use ActionMailbox

2.13 HTTP Requests

This might be handy for downloading from Webpages or APIs

  • gem curb - the http library curl for ruby

2.14 Using APIs

2.15 Geo Information, Geocoding

sometimes you want to convert longitude/latitude coordinates to street addresses, or the reverse

Use postgres's inbuilt geographical features:

2.16 PDF, Excel, csv, ...

2.17 Testing

2.18 Understanding your Code better

better_errors screenshot

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