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[SOUND] Hi, I'm Jason,
your Treehouse Ruby teacher.

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In this course we're going to
be going over modules in Ruby.

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If you've been following along
with other Treehouse Ruby courses

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you've already come across and used
modules, although you may not know it.

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If you haven't, don't worry.

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We'll be doing a little bit of
a refresher about classes and

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how they relate to modules.

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The two share some very
special similarities.

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In Ruby, a module is kind of like a class
or object in that it's its own thing.

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Modules are used for
a few different purposes, containers,

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behaviors, and occasionally, storage.

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One of the most common uses of modules
in Ruby, is adding behavior to classes.

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Let's take a game as an example.

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If we're building a game that had
robots that could shoot laser guns, and

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as we're coding the game, we give
the robots methods like LaserBlast,

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LaserDamage, DrawLaser and more.

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Later on, as the game design progresses,

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we decide that we have a few
more kinds of characters.

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Like sharks that need to shoot lasers also
because it's a crazy world out there,

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and they were jealous of the robots.

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We could take all of the methods from the
robot class that have to deal with lasers

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and put them into a module.

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And we could call the module something
like uses laser blaster, and

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that's where we could keep
all of that behavior.

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If we were to include the,
uses LaserBlaster module,

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in the shark class, it would now
have access to all of those methods.

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When we do that,
it's called using a module as a mix in,

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because we're literally mixing
in behavior to a class.