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We have already used it some in previous lectures, but just to refresh.

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Let's see one really quickly.

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So we'll create a vector and we'll use the macro and we'll just say one, two and three.

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And it helps if I use the correct brackets.

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And then we can say for Val and Vic dot ed.

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Print line and then print the vowel that is in the iterator.

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So we'll say cargo run and we see one, two, three being printed out.

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So all integrators are going to implement a trait named Iterator which is defined in the standard library.

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The trait looks like this.

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So we have trait iterator.

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And then we're going to have type item and then we have effin next.

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Which is going to be a reference to the mutable self and it's going to return an option of self item.

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And then there's many default methods available to us once we implement next.

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So item is the type of value the iterator produces and the next method either returns a sum with a value

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contained in it, or it's going to return none to indicate the end of the sequence.

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And then we also have the end to iterator trait.

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And any type that implements in to iterator is an iterator because it's something we can iterate over

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by calling the end to enter method.

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So let's look at an example of this and I'm just going to comment that out.

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And we'll comment this out as well.

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So we'll create another VEC called VEC two and then here we'll do the same thing one, two and three.

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And then we'll say let mute editor equals a reference to our VEC and then we'll say into.

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Bitter.

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And then while.

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Let some V equal it to next, which is the method given to us here because we created an iterator this

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way.

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By calling the intuitive method, we can now print out the values inside of some V, and if we run this,

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we expect the same output of one, two and three grade, which is exactly what we got.

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So just to clarify, an iterator is any type that implements the iterator trait and and iterable is

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any type that implements into iterator.

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Now remember last lecture?

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I said closure sign when using iterator.

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So let me expand on that.

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So we will comment all of this out.

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And up here, I'm also going to just go ahead and comment.

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All of this out.

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As well as that.

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And as well as.

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These.

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So I want to create a new struct called item.

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And in here I want it to be.

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String that has a name.

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And we're also going to give us the drive debug trait here as well.

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So now we're going to create a function that's going to be called check inventory.

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And we're going to accept a vector of items.

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And then we want to check to see if a product exists by accepting an A string.

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And then we'll return back a vector of item.

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And then in here, we want it to be items into.

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Ed so create an iterator and then we want to filter.

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So now we have another iterator.

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So as we see here, it creates an iterator for us.

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And this is where our closure is going to really help us.

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So we'll accept an a parameter and then we want to check to make sure that name equals a product and

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then to return it back to us in a vector we want to collect on this.

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So in here we'll create a vector of type vector item, which is going to just be a new vector.

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And so now we'll push in some values.

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So we'll push in an item.

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And then in here our name is going to be a string from and we'll have a coat.

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In this case.

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So now let's push in a couple more additional items.

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We'll have a and we'll add in our semicolons.

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And I will add have a shirt.

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We'll have some shorts and we'll have some shoes.

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So, again, a very simple little example for us to kind of understand what's going on.

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So then we'll say get checked equals check inventory.

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We'll pass in our VEC and then we want to make we want to see if we have a string from shirt.

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So we want to see if we have a shirt in stock in our inventory and then we will print out.

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What is returned to us.

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So let's run this and just see what happens.

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So we see that we have an item with the name shirt return to us.

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So let's go back up here and kind of look at what we did.

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So we use an end to iterate, to create an iterator that's going to take ownership of the vector, and

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then we call filter to adapt that iterator into a new iterator that only contains elements for which

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the closure returns.

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True.

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The closure captures the product parameter from the environment, and it's going to compare the value

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with each item we created and only keeps the item we specified, which in this case was a shirt.

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So it's only going to keep the item.

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There's a shirt.

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And then we call collect to gather the values returned by the adapted iterator into a vector that will

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be returned from the function.

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So we used a closure in this case to quickly evaluate logic without having to do a separate function

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call, which allows us to keep our code clear and concise.

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So that is one of the ways that a closure really shines.

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When we use iterator, we're able to quickly and efficiently have short and concise logic in order to

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evaluate.

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Values coming into our closure.

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But now what if we wanted to create our own closure?

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Excuse me?

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Our own iterator.

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So we'll create another struc.

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And we'll call this one arrange and we'll give it a start and then it'll be unsigned 32 and then we'll

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give it an end of unsigned 32 as well.

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And now remember, we have to implement an iterator for range and now we need to implement the trait.

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So we're going to have type item and it's going to be unsigned 32 and now we need to implement next.

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So we'll have a mutable reference to self and it's going to return an option of self item.

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Is that how it was?

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So self item.

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And here we will say if self start is greater than or equal to self end, then we want to return none.

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Otherwise let result equal some self.

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Don't start.

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And then sell, start, increment it by one and then give us the result.

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So to check to make sure that this works for us.

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Let's create a range

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and we'll give it a zero to start and then we want our end value to be ten.

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And they will say four are in range.

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If we want to print out.

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Iterator and we want this to be a little.

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Ah.

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So now if we run this and we now see zero one, two, three all the way to nine, which is perfect.

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So now we know that our iterator is working for our range struck.

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So I also said that we should get some default traits or excuse me, some default methods once we implement

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in the next function.

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So let's check to make sure that we did that.

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And then that would also prove that we got our.

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Implementation done correctly.

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So we're going to call range dot filter, which is a function given to us.

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If we implement NEX correctly, we're going to pass in a parameter and we only want values where when

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that parameter modded by two equals zero.

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So that means when the the values divided by two are remainder is zero and then we want to collect that

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way it is stored inside of our vector.

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And now if we print this vector out, we would expect all the values that when divided by two equals

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zero.

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And we see that we get 02468, which is correct.

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So that's really all there is to it.

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For integrators and closures, we see that we can use closures to allow us to easily perform logic on

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values inside an iterator.

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In the next section, let's continue on and start learning about smart pointers.