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Enumerable is one of the most
widely used modules in Ruby.

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We could do a whole course just
on the Enumerable module, but

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we're only gonna take
a quick look at it today.

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The Enumerable module is
going to be very familiar.

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It gives us methods that we've
worked with in arrays and

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hashes such as map, include, and find.

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Let's take a look at how Enumerable
works now using Work Spaces.

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So, let's go ahead and
quickly launch an irb console and

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just take a look at this hash.

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So, just gonna create a regular
hash right here with two keys.

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And two values, saying my name is
Jason and my location is Treehouse.

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Now, we've worked with hashes a little bit
before during the Ruby curriculum, but

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let's just do a little refresher here.

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If we want to know if a hash has a certain
key, we can use this include method.

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And then, pass it the key that
we wanna see if it's there.

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So, if we look at name that's there,
if we look at location that's there,

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if we look at age, that is not there.

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And then, we have a few more
methods that we can work with.

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We could ask the hash if any of the items,
keys or values.

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The value is equal to Jason and
we get true.

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Or, we could ask the hash
if all of the values,

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Are Jason, and we get false.

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And then we could even do something
like selecting all of the different hash

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values, where the value's
length is greater than five.

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And we only get that one hash key and
value back.

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Now this a little bit of a refresher.

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If we look at the documentation for
Ruby Hash we can see

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that some of these here,
like each key each pair or

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even include, it returns true if
the given key is present in the hash.

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All of these methods come
from this Enumerable module,

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or the Enumerable mixin.

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Now what's really nice,
is since Enumerable is a module,

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we can include Enumerable
in our own classes.

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And then get access to all
of those methods ourself.

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So all these methods like any,
all, include, and

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find, find all, select,
those are all part of Enumerable.

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Let's go ahead and see how that works.

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If we read the documentation, it says the
class must provide a method called each,

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which yields successive
members of the collection.

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So I'm going to go ahead and
exit out of IRB here and clear the screen,

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and I'm going to open up
this enumerable.rb example.

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Now if we look at this
code this has two classes,

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a player and a game and
these are really simple.

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The player class includes
the comparable module and

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defines that spaceship operator
with the player's score.

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And it has two attributes name and score.

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Now we also have this game class and
the game class has players.

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It sets players to an empty array
when the game is initialized and

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then we can use the add player method
to push players onto that array.

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And then we can also get the score of
this game, it just assembles the score of

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all the different players, so
I've created a couple different

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game instances here and a few different
player instances with different scores.

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Game1 has two players.

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Game2 also has two players.

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So we're just gonna run this and
see what the game looks like.

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And we see we got this game instance and
it's got an array of players.

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So now let's go ahead and
implement the Enumerable module.

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And what we want to do is iterate
through all of these game's players.

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So, we can say game1.any.

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We want to have access to this any method.

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We'll say player.

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Player.score is greater than 80.

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Now we know this should return true
because Kenneth only has 80 points.

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We want greater than 80.

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But Jason has 100 points.

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Not trying to brag.

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Now if I were to run this right
now we would see this fail out.

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And it says undefined method any for
this game.

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And that's because we haven't
included Enumerable yet.

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So if we do that, we include Enumerable,
and we're gonna run this and

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it's going to fail again.

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Clear my screen there, and
it says undefined method each for game.

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So let's go ahead and
implement this each method.

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If we were to back to the Enumerable
documentation, we can see the class must

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provide a method called each, which yield
successive members of the collection.

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So we'll go ahead and
define this each method.

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And we're gonna do something
a little bit advanced here.

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We're gonna say that each
method takes a block, and

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we're going to say that
just goes out to players.

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Now, remember players is an array,
so it has this each method.

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And all we are doing is passing this
block as a variable to that each method.

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This is called pretzeling, and we're just
passing around this block like a variable.

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So once we do that,

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this any method that we have at
the bottom here should start working.

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And let's go ahead and print that out.

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And it looks like we get true, so one of
the players does have a score above 80.

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Now since we defined this each method,
we now have access

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to all of these different
methods inside of Enumerable.

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And it makes it very very powerful.

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So we could do any, we could find
all of the different players.

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So let's go ahead and do that.

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Let's go ahead and
say players is game1.find_all player.

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Player.score is greater than 80.

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[SOUND] And
then let's put there's with base score,

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greater than 80 and
inspect that player's variable.

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Al right, and find all returns an array.

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If we just wanted to find the first one,
we could change that to find.

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And then if we run that again, we can see
it just returns one player instance and

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does not have an array.

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On your own, go ahead and check out this
documentation and try playing around

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with a bunch of different methods
inside of the Enumerable module.

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There's a link in the documentation and
go ahead and

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try checking out Detect,
Collect, Any and All, and

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all of those different methods,
and give it a try in Work Spaces.