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[MUSIC]

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In Ruby, a Gem is a library that contains
a specific piece of functionality

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as well as any files or
assets related to that functionality.

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Gems can be found for all sorts of
common things that you'd want to do

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in an application, things like handling
money and currency, integrating with

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credit card processing, tools to make
Ruby coding even easier, and more.

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You could write these things yourself,

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but one big benefit to using a Gem
instead is that it saves time.

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The main place that gems
are found is rubygems.org.

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Let's take a quick look at RubyGems now.

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Now here we have the main
rubygems.org website.

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Now the instructions on
here are pretty clear.

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You can find, install, and
even publish your own RubyGems.

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Now, the main focus of this
site is the big search

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box right in the center of the screen.

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This is how you'll find most of
the Gems that you want to work with.

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Let's say we wanted to install a Gem
to work with money and currency.

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We can search Gems and find money,
if only it were that easy in real life.

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Now once we search,
we see any exact matches for

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Gem names that come up and then, a small
description of what the library does.

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Here, we see it's a Ruby library for
dealing with money and

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currency conversion.

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Over on the right-hand side of the screen,
we'll see the number of downloads.

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Now this can be a good indicator of
the popularity of a particular Gem.

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Gems with more downloads
will be more popular, and

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it can be reasonably assumed that they're
maintained more often than other Gems.

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Now as we scroll down this page,
we'll see less exact matches and

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these results are paginated, so

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this is only displaying one through 30,
of 134 total Gems.

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Now as we scroll down,
we see the less exact matches, money-rails

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provides integration of Ruby
money in a rails application.

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Once we find a Gem that we want,
we can click into it and

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see a more thorough description.

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On the left side,
the most recent versions will be shown.

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Now we can see that this Gem
is up to version 6.6.1, and

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the most recent version was
released on July 27th, 2015.

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If we click in, we can see all of
the different versions of this Gem,

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and it was released
originally on June 8th, 2005.

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So this Gem has been released and
maintained for about ten years.

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On the right side of the screen, we have
runtime and development dependencies.

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A runtime dependency will
only be installed if the Gem

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needs to be used in an application.

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So we can see that the Ruby Money Gem
depends on the i18n Gem.

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i18n stands for internationalization.

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Now we only need that gem to be installed
as well if we're just going to use

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the Money Gem.

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However, you'll see below that,

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there's a development dependency
section of the screen and

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this shows that the Gem depends on
bundler, kramdown, rake, rspec, and yard.

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We only need to worry
about those if we plan

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on doing development against this Gem.

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In order to just use it,

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all that we would need installed
besides the Gem itself is i18n.

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When we install the Gem,

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any dependencies that are needed
at runtime will also be installed.

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We'll learn a little bit
more about that later.

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Now we can also see if we click back to
the homepage, there's a stats section.

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If we click in there,

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we can see the most popular Gems that
have been downloaded on rubygems.org.

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This is based on the total
number of downloads and

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we can see the most popular Gem is Rake.

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Rake comes with Ruby and is a task runner.

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The scope of Rake is a little
bit outside of this course,

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but it is one of the most
popular Gems as well as Rails.

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You may have heard of Ruby on Rails.

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Now if there's another functionality
that we want, we can search for Gems.

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Let's say we want to use a Gem for
interpreting JSON outside of the standard

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library, well, we could search for
and find many different JSON Gems.

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And then we could click into them and read
a little bit more about them if we want to

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and make the determination about whether
or not we wanna use these in our programs.

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Another source for
finding Gems to work on is Ruby toolbox.

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The Ruby toolbox shows Gems
by category and popularity.

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We could click on the categories section,
and it will have by name and by group.

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So for example, if we were looking for
a different testing framework,

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we could click in to the testing
framework section and then,

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Unit Test Frameworks and this will
show us ranked by order of popularity,

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the different Gems that are available
as a testing framework.

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We can see that the RSpec Gem
is one of the most popular.

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It had it's first release about
seven years ago, and the most

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current version was released about a month
ago, as of the time of this recording.

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It will also show the number of
watchers and forks on GitHub.

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As we scroll down,
we see other testing frameworks as well,

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and the description of the Gem
is right below the Gem Name.