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Extend and Include
4:14In this video, we learn a little trick with extending and including something at the same time.
When we last left off,
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we had just added the stock_count
methods to our inventoriable class.
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Now what we're gonna do is take the same
pattern that we used in the tracking
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module to do this create and
return instances.
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So, we're gonna do this
in a tricky little way.
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We're gonna do it inside of another
module, inside of Inventoryable.
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We're gonna call this ClassMethods
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because these are going to go on
the class of what we want inventoried.
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So let's go ahead and
write our create method.
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And that's going to take
an attributes hash.
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And this is gonna be very very
similar to what we did here.
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We're gonna initialize an object, push
it to instances and return the object.
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And the only difference between this and
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the create method in the tracking
module is that we're
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taking an attributes hash instead of
a single item, which was a string.
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So now we'll be able to say, shirt.create.
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But we still need to write
the instances method.
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Very very easy, we just say, instances
conditionally equals a new array.
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And now we can push on to that.
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So, we've got this class methods module.
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And what we need to do
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is extend our shirt class with
it in order to get that to work.
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We can say extend
Inventoryable::ClassMethods,
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and now we'll get
the create method as well.
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So we can say the same thing here,
Shirt.create,
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Shirt.create, and this shouldn't affect
our code at all, and it should work.
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Let's go ahead and
run it and see what happens.
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Okay, it looks like we got
what we were expecting.
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We still have these
specific shirts in stock.
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New.
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Take all of these out here,
and let's go ahead and
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just take a look at Shirt.instances.
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Just to make sure everything is in there.
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So I'm gonna clear my screen and
run that again.
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And we can see we have these
two instances of the shirt
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class just like we expected to
by having this create method.
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So this is kind of cumbersome
to keep doing each time.
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Extend and include.
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And, there's a pattern that a lot of Ruby
programmers use when we do something
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like this.
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Now, remember this included method
that we had access to before?
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Where we sent in the class
that's been included?
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We could take advantage of that inside
of our Inventoryable module as well.
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So when we say that this module
has been included into this class,
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we can get really tricky and
just tell the class to extend itself
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with the class methods that
are inside of this module.
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Now, if we take this out,
everything should still work.
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I clear my screen and run this again.
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We still get these shirts and
the create method works fine,
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even though we're only
specifically including one module.
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So when we include it, the class gets sent
in, which in this case is the shirt class.
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So by calling shirt.extend ClassMethods,
it's the same thing
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as if we extended it with
the Inventoryable class methods ourselves.
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