What Are Ruby Gems?

[MUSIC] 0:00 In Ruby, a Gem is a library that contains a specific piece of functionality 0:04 as well as any files or assets related to that functionality. 0:09 Gems can be found for all sorts of common things that you'd want to do 0:14 in an application, things like handling money and currency, integrating with 0:17 credit card processing, tools to make Ruby coding even easier, and more. 0:22 You could write these things yourself, 0:27 but one big benefit to using a Gem instead is that it saves time. 0:29 The main place that gems are found is rubygems.org. 0:34 Let's take a quick look at RubyGems now. 0:37 Now here we have the main rubygems.org website. 0:41 Now the instructions on here are pretty clear. 0:45 You can find, install, and even publish your own RubyGems. 0:47 Now, the main focus of this site is the big search 0:53 box right in the center of the screen. 0:56 This is how you'll find most of the Gems that you want to work with. 0:59 Let's say we wanted to install a Gem to work with money and currency. 1:03 We can search Gems and find money, if only it were that easy in real life. 1:09 Now once we search, we see any exact matches for 1:16 Gem names that come up and then, a small description of what the library does. 1:20 Here, we see it's a Ruby library for dealing with money and 1:25 currency conversion. 1:29 Over on the right-hand side of the screen, we'll see the number of downloads. 1:32 Now this can be a good indicator of the popularity of a particular Gem. 1:36 Gems with more downloads will be more popular, and 1:41 it can be reasonably assumed that they're maintained more often than other Gems. 1:44 Now as we scroll down this page, we'll see less exact matches and 1:50 these results are paginated, so 1:55 this is only displaying one through 30, of 134 total Gems. 1:58 Now as we scroll down, we see the less exact matches, money-rails 2:04 provides integration of Ruby money in a rails application. 2:09 Once we find a Gem that we want, we can click into it and 2:15 see a more thorough description. 2:18 On the left side, the most recent versions will be shown. 2:19 Now we can see that this Gem is up to version 6.6.1, and 2:24 the most recent version was released on July 27th, 2015. 2:29 If we click in, we can see all of the different versions of this Gem, 2:34 and it was released originally on June 8th, 2005. 2:40 So this Gem has been released and maintained for about ten years. 2:45 On the right side of the screen, we have runtime and development dependencies. 2:51 A runtime dependency will only be installed if the Gem 2:57 needs to be used in an application. 3:01 So we can see that the Ruby Money Gem depends on the i18n Gem. 3:05 i18n stands for internationalization. 3:11 Now we only need that gem to be installed as well if we're just going to use 3:15 the Money Gem. 3:19 However, you'll see below that, 3:20 there's a development dependency section of the screen and 3:22 this shows that the Gem depends on bundler, kramdown, rake, rspec, and yard. 3:26 We only need to worry about those if we plan 3:33 on doing development against this Gem. 3:36 In order to just use it, 3:41 all that we would need installed besides the Gem itself is i18n. 3:42 When we install the Gem, 3:47 any dependencies that are needed at runtime will also be installed. 3:49 We'll learn a little bit more about that later. 3:55 Now we can also see if we click back to the homepage, there's a stats section. 4:01 If we click in there, 4:06 we can see the most popular Gems that have been downloaded on rubygems.org. 4:07 This is based on the total number of downloads and 4:12 we can see the most popular Gem is Rake. 4:15 Rake comes with Ruby and is a task runner. 4:19 The scope of Rake is a little bit outside of this course, 4:23 but it is one of the most popular Gems as well as Rails. 4:28 You may have heard of Ruby on Rails. 4:33 Now if there's another functionality that we want, we can search for Gems. 4:38 Let's say we want to use a Gem for interpreting JSON outside of the standard 4:42 library, well, we could search for and find many different JSON Gems. 4:48 And then we could click into them and read a little bit more about them if we want to 4:54 and make the determination about whether or not we wanna use these in our programs. 4:59 Another source for finding Gems to work on is Ruby toolbox. 5:05 The Ruby toolbox shows Gems by category and popularity. 5:10 We could click on the categories section, and it will have by name and by group. 5:16 So for example, if we were looking for a different testing framework, 5:23 we could click in to the testing framework section and then, 5:27 Unit Test Frameworks and this will show us ranked by order of popularity, 5:30 the different Gems that are available as a testing framework. 5:37 We can see that the RSpec Gem is one of the most popular. 5:41 It had it's first release about seven years ago, and the most 5:46 current version was released about a month ago, as of the time of this recording. 5:49 It will also show the number of watchers and forks on GitHub. 5:54 As we scroll down, we see other testing frameworks as well, 5:59 and the description of the Gem is right below the Gem Name. 6:02