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‫And this video, we're going to look at some very important interfaces that you should understand once

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‫you want to become a more advanced shop developer.

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‫And that is the AI enumerable interface as well as the AI enumerator interface.

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‫So you should understand interfaces before watching this video, because otherwise some of the concepts

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‫won't make sense to you potentially.

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‫So I really recommend to check out that the interface video that we have to offer as well.

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‫Okay.

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‫So the AI enumerable interface is the base interface for many collections in C sharp and its job is

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‫to provide a way to iterate through a collection.

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‫So this is why we can use for each loops to go through a list or a dictionary because they are inheriting

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‫from the enumerable interface.

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‫So the enumerable interface in simple English, when the collection class implements the AI enumerable

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‫interface, it becomes countable and we can count each element in it individually.

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‫So there are two different versions of the AI enumerable interface.

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‫One is that works for generic collections where you have this AI enumerable opening bracket, closing

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‫bracket, and then the AI enumerable interface for non generic collections.

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‫So you should understand what generic and non generic collections are as well.

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‫They have certain advantages and disadvantages, but I have a video for that as well.

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‫I hope you watched it before watching this video because otherwise it's a little complicated.

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‫Okay.

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‫So these two that we have here, let's look at those.

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‫Since the generic collections were introduced after the non generic collections, it's recommended to

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‫use the generic collection.

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‫So they are basically an improved version, so to speak.

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‫So if you are creating a new project, it's recommended to use the generic version because an I enumerable

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‫for non generic collections needs to apply or perform boxing and unboxing, which basically is the conversion

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‫of types of objects.

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‫And we will later explain how to use the AI enumerable tty interface.

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‫So the generic collections interface, we're not going to go over the non generic collections interface

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‫because it's not recommended due to the boxing and unboxing, which just is less efficient.

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‫So now let's look at the difference between the AI enumerable and the AI enumerator.

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‫You maybe have heard those before.

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‫So the AI enumerable interface contains a single method that you must implement when implementing this

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‫interface, and we're going to do that later on in our particular example here.

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‫So it makes a lot more sense.

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‫So the get enumerate method is the one that you need to implement and it returns an AI enumerator object.

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‫So this method that you need to implement when you want to use a AI enumerable for your class or what

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‫you want to implement it for your class, you need to have this get enumerator method which then returns

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‫an AI enumerator.

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‫So the AI enumerator.

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‫Provides the ability to reiterate through the collection by exposing a current property that points

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‫at the object we are currently at in the collection.

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‫This is a lot more complicated than it will be once we actually run this in our particular example.

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‫So we're going to build an example fully understanding what all of this means.

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‫So this is just to prepare you what you can expect.

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‫Okay, so let's get started.

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‫Finally getting away from all of this theory, let's actually look into practice.

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‫So let's create this little class called dog.

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‫And I'm going to put it in the same file to keep things simple.

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‫So we have this class called Dog with a name and we have this Boolean called is Naughty Dog.

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‫So we will basically check if the dog is naughty or not.

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‫And based on that, we are going to give him treats.

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‫So if he's not a naughty dog, he will get less treats than if he's a good boy or a good dog.

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‫So the constructor here basically just sets those two values.

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‫So when we create a dog object, we are going to give it a name and a boolean, whether the dog was

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‫naughty or not.

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‫And then we have this gift treat method and this will basically just print out the dog said Woof.

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‫So for every single treat that the dog is given, he will say Woof.

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‫So basically, if he's a good dog, you will get two treats and he will move twice.

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‫And if he's a bad dog or a naughty dog, then he will only move once because he will get less treats.

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‫Okay.

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‫So now we have this class dock and we can now go ahead and create dog objects.

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‫So let's have this other class.

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‫Let's assume we have another class that will use dogs inside of a list.

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‫So we have this dog shelter class.

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‫So this dog shelter class will have a list of dogs.

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‫So therefore we need to make sure that we have this using system collections generic because list is

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‫a generic collection.

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‫So here at the top you will see that now you have this using system collections generic.

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‫Okay.

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‫So now that we have this dog shelter and we have this list of dogs in the constructor of this dog shelter,

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‫the only thing that we're going to do is to initialize this dog's list with a bunch of dogs.

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‫So we have the Casper dog or a dog called Casper.

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‫He's not an old dog, but if is a naughty dog, Oreo is not naughty and Pixel is also not naughty.

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‫So don't ask me how we come up with these names, but that's basically how we're going to call those

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‫dogs.

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‫You could, of course, make this whole application a lot more complex, but our idea is really just

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‫to use this list of dogs to iterate through the dog shelter, to go through the dog shelter, basically.

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‫And based on whether a dog is good or not or a naughty dog or not, we're going to give him one treat

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‫or two treats.

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‫So now let's go over to our main method, because that's where our starting point of our application

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‫is.

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‫And at this point, let's go ahead and create a dog shelter here.

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‫All right.

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‫So we have this dog shelter called Shelter, and it will be a new dog shelter.

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‫So we initialize it straight away as well so that we can use this shelter object because the shelter

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‫object will contain a list of dogs.

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‫Right.

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‫So now what we want to do is we want to iterate through the list and check if we want to give them treats

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‫or not.

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‫So let's create a for each here like so double tab in order to prepare it for us.

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‫So what is it that we are going to go through?

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‫Well, we are going through a dog.

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‫And we're going to call a dog.

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‫So every single item inside of the list will be a dog.

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‫And then the collection that we want to go through is, in fact, going to be the shelter.

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‫Like.

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‫So now we have a little problem.

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‫Once we hover over it, we say we see here name of collection or array to iterate through is the shelter,

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‫but the for each statement cannot operate on variables of the type dog shelter because dog shelter does

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‫not contain a public instance or extension definition for get enumerator.

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‫Okay, so there we have this get enumerator.

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‫So what does that mean?

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‫Well, this means that we need to implement the interface I enumerable right here for our dog shelter

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‫because this dog shelter has a list that we want to iterate through.

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‫Right?

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‫Because if you look at it, shelter, well, our dog shelter, that's the shelter that we want to iterate

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‫through.

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‫And in order to make it iterable, we need to implement the AI enumerable here.

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‫And what type of objects do we want to enumerate?

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‫Well, in our case, it's going to be the dogs.

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‫So we want to be able to go through the dogs inside of the dog shelter because, well, we have this

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‫list dogs and it's initialized here in the dog shelter constructor.

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‫And we want to make sure that we can just go through all of them and do something with the dogs, like

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‫pet them or in our case, give them a treat.

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‫So once you implement this and you go up here, the error disappears.

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‫So suddenly it's fine because, well, our shelter, which is a dog shelter, now follows the instructions

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‫that were just given to us that it needs to implement it.

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‫I enumerable here.

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‫So this is the generic I enumerable because we have this doc right here.

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‫Right?

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‫Because it's not this one.

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‫It's the one with the type that we're giving to it.

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‫But now, once we hover over it, we see we get another error.

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‫It says doc shelter does not implement interface member.

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‫I enumerable doc get enumerator and the I enumerable get enumerator so we can manually put them in there.

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‫But the beauty about using an ID is that the ID can do a lot of work for us, so you can click on show

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‫potential fixes and then click on implement all members explicitly and it will then add the collections

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‫namespace for us and it will take care of adding those two methods for us or those two members.

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‫So once we click on this, you see that this error will disappear.

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‫And if we scroll further down, you will find that now we are returning an enumerator of type doc and

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‫a non generic I enumerator collection.

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‫So now we haven't implemented it.

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‫That's why we have this throw new not implemented x exception here.

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‫So we need to change that here.

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‫We can now implement what should happen with our get enumerator method once it is called.

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‫So in order to fix it, what we're going to say here is just return.

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‫Dogs our list dogs dot get enumerator just like so.

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‫And that will be the implementation because our dog shelter is now implementing the enumerable interface.

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‫And our list here is, in fact, A, if you hover over it, a list is a generic list.

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‫And now we can take these list dogs and we can get the enumerator for every single iteration that our

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‫for each group will go through.

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‫So basically it will return the individual dogs.

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‫And now what we can do is we can actually use the dog in our for each loop here.

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‫So that basically means that we can now go ahead and check if the dog is not naughty.

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‫So not dog dot is naughty.

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‫If that's the case, that basically means if the dog is not naughty, we are going to call the method,

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‫give treat, and we're going to give him two treats.

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‫And otherwise, if he was naughty, because we can't not give treats, we just love dogs too much.

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‫We are just going to give them one treat like so.

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‫And at this point, we can run our application.

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‫And we will see.

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‫Casper said Wolf two times, because he's a good dog, sniff is a naughty dog, so he gets only one

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‫treat and he says, woof, once Oreo does it twice and pixels move twice as well.

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‫All right.

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‫And that is basically how you can make your class follow the instructions or implement an AI enumerable

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‫so that you can loop through a list using the for each loop, for example, as we have it here.

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‫Now, you might wonder, why are we not implementing the gate enumerator with the AI enumerable, the

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‫one that is non generic?

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‫Well, that's because we don't use a non generic example and our dog shelter is not non generic either,

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‫but it's just that you need to implement it when using the AI enumerable interface because otherwise

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‫if you get rid of it, we will get a warning here again.

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‫You see here, we're actually in error, so we need to make sure that we have this method in there as

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‫well.

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‫All right.

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‫So that's it for this video.

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‫And the next video, we are going to look at another example where we are going to take advantage of

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‫the eye, innumerable even more.

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‫So this was just a little bit of an introduction.

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‫I know this topic is rather complex and complicated, but we're going to take advantage of them a little

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‫more.

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‫And now, by the way, just a quick one, just a summary here.

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‫When is it recommended to use the AI enumerable interface?

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‫Well, you should use it when your collection represents a massive database table.

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‫So you don't want to copy the entire thing into memory and cause performance issues in your application

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‫because the database could be huge, right?

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‫It could have millions upon millions of entries.

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‫And you don't want to have to load the whole thing to iterate through it, but you just want to load

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‫as much as you require for the current process, whatever you want to execute.

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‫And then when should you not use the AI enumerable interface?

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‫Well, when you need the results right away and you are possibly mutating, editing the objects later

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‫on.

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‫In this case, it is better to use an array or a list.

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‫So when you want to be able to mutate or edit objects later on and you don't need the result straight

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‫away, use an array or a list.

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‫Otherwise use an AI enumerable because it's going to be more efficient.

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‫All right.

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‫So that's it for this video.

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‫See you in the next one.