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Just like strings and

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numbers, Ruby gives us a lot of methods
we can use to work with hashes.

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These methods can operate on keys and
values at the same time.

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Let's take a look at how some of
them work now, using work spaces.

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Okay, now that we know how to create and
work with hashes, let's go ahead and

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start learning about some
different hash methods.

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And I'm gonna create a file for this and
we're gonna call it hash_methods.rb.

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Now let's go ahead and
set up a hash to work with.

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And we'll have the keys of hash,
"item", and that's "bread".

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And we only want one.

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And the brand is "Treehouse Bread Company".

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Okay, now, let's go ahead and
just print out the hash.

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Let's just run this and make sure
everything is working and nothing's crazy.

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So click down into the console, and
type ruby and then hash_methods.rb,

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and there is a printout of our hash.

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Now I'm gonna get these hash methods
from the Ruby Hash documentation.

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Some of the methods that we're going to
look for here, the first one is length.

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And that will return the number
of key value pairs in the hash.

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Let's go ahead and see how that works now.

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And we'll just say hash dot length.

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And print it out.

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And let's run this again and
see what happens.

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All right, the hash has a length of three.

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And you know what let's
change that to print.

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So it's all on the same line.

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Clearing my screen on the bottom
there with Ctrl+L, and there we go,

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we have a length of 3.

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Another neat method is
something called invert and

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that will transpose the keys and
values into a new hash.

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And let's go ahead and
print that to the screen as well.

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I'm gonna save that and run that again and
now if we look, here's our original hash.

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But when we run the invert method,
it changes all the keys and values.

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And it does not change the original hash.

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The next method that we can
take a look at is called shift.

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Now if I click on the methods list
here in the hash documentation.

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This will remove a key value
pair from the hash and

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return it as a two item array
with the key and value.

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Let's go back to our workspace and
see how that works.

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So we're gonna print out the hash
after shifting it as well.

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And we can use the inspect
method to print out the hash.

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Let me clear out my screen on the bottom
again, with Ctrl + L and run this again.

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Now, we've called hash.shift and
this returns "item" and

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"Bread" in an array form, but
are we really sure it's an array?

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Let's go ahead and call the inspect
method on that to make sure.

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So when we run that again,
we can see this comes back as an array,

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and our hash now does not have
the item "item" as a key.

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Let's go ahead and
put the item back in the hash.

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So we'll say item hash["item"] is "bread".

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Now let's go back and
look at some more methods.

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The last method that we're
gonna look at is called merge.

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Now merge gives an argument of
another hash and returns a new hash.

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That sounds a little confusing, so
let's go ahead and see how it works.

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And we can just print this out now.

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So here's our hash, let's print that out.

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And now, let's print this out and
merge it with a couple other hashes.

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Now we call the merge method and
then we pass in another hash.

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And then we'll go ahead and

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print the original hash out again,
just to see what it looks like.

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Clear my screen since this is getting to
be a lot of output and we'll run it again.

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So now we've printed out Merged
with this particular hash and

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what we get back is a new hash.

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You know what,
that's a little hard to read.

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Let's change this to puts and
run it again.

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So here's our original hash.

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Now we merge it with calories of 100 and
we get back this hash,

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which contains another hash with calories
of 100 added on to the original hash.

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But, if we look back at that original
hash, it does not have the calories key.

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This is because merge
will create a new hash.

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Now you might wonder what would happen,

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if we called merge with a key that
already exists inside the hash.

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Let's go ahead and see what happens.

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And we'll just merge that
with a different item name.

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Now let's clear the screen here and
run it again and see what happens.

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Now when we do it,
we'll see that the new hash comes back

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with only one key of "item" 
which points to "Eggs".

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Which is the last thing that
we called in with merge.

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When merge has a conflicting hash key,
the hash that's sent into merge

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receives precedence and will overwrite
the existing key value pair.

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Using the documentation linked in the
teacher's notes section of this video, try

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looking up and practicing with different
hash methods on your own using workspaces.