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RubyGems does a few
tricks when using a gem.

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First off, gems are installed to
a specific place on the file system.

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This is usually your Ruby installation
location, but it can also be changed.

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Ruby then needs to modify the load path
very slightly to take the gem location

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into account.

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Let's take a look at the gem
environment now using workspaces.

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If we take a look at our file system here,

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we can see that we have money and
money example.rb.

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If we go up a level, we can see
that there is a .local directory.

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Now this is something that
is work space specific.

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So if I type Gem environment, we can see

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that /home/treehouse/.local/gems
is in our path.

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This is where gems are installed
to in a workspace.

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We can see if we go into
the gems directory.

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We have our bin directory,
build info, cache, extensions, doc,

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gems and specifications.

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This is where any gems that we
install will go on the file system.

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So here is the gems directory.

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And we can see the different names
of the gems that we have installed,

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followed by their versions.

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And you'll notice this corresponds
to our gem list command.

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And the gems that don't
come with Ruby by default

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are going to be installed right here.

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So I'm gonna clear my screen here for
a second and go into irb.

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Now, when Ruby is loading
a file it looks for

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it in a special variable
called the load path.

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And we can actually look
at the load path right now.

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That's a constant that's going to be
inside of every Ruby application.

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And we can see the different places
that Ruby searches for files to load.

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Now, if we tried to use
the Money gem right now,

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You'll see we get
uninitialized constant money.

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But, when we require it.

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This is all of a sudden, loaded and

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we have access to the money class,
because of the money gem.

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So let's keep these load paths in mind for
a second right now,

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and I'm going to clear my screen.

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And print the load path
to the screen again.

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And you can see once we do that, Ruby
has added to the front of this load path

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array the money gem location and
any of its dependencies.

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Now as a file naming structure in a gem,
most of the gem's library files

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are in a lib directory below
the main gem directory.

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And that is what gets
appended to the load path.

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Since Ruby searches the load path for

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different files to load, it now
knows to look in these places first.

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So, require will search
your ruby gems location for

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the name of the gem, and
then take the most recent version and

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append the lib directory
if the gem exists.