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‫In this video, I want to, very quickly,

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‫refactor the API features that we've implemented

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‫over the last couple of lectures.

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‫Now, this is not only to make our code a bit cleaner,

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‫it's also to make it more modular and more reusable

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‫in the future.

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‫So, right now, we have all this code for the features

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‫that we built before in this getALLTours function, right?

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‫And this looks a bit messy.

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‫It's a bit hard to understand, okay?

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‫And, also imagine that we wanted to use these same features

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‫for another resource.

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‫For example, for the users or, later, for the reviews.

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‫It would be not very practical to, basically,

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‫copy the code from here and use it, then,

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‫in the other resources, right.

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‫And so, what I'm going to do is to, now,

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‫create a class in which I'm going to add one method

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‫for each of these API features or functionalities,

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‫as you might call them as well.

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‫All right?

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‫So, let's go ahead and do that here

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‫and I'm going to do it here, for now, then, later on,

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‫I'm actually going to export it to its own file,

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‫basically, to create a reusable module that we can,

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‫later on, import into other controllers.

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‫All right?

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‫So, class, and I'm calling it APIFeatures.

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‫All right.

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‫Then, we start with our constructor function

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‫and remember that this is the function that gets

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‫automatically called as soon as we create a new object

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‫out of this class, all right.

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‫Now, what do I actually want in these API features?

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‫Actually, I'm going to parse in two variables here, okay?

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‫So the mongoose query and also the queryString

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‫that we get from express.

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‫So, basically, coming from the route, all right.

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‫So that's what we usually have access to

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‫in the req.query, okay.

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‫Now, again, I'm passing the query here because I do not

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‫want to query inside of this class because that would then

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‫bounce this class to the tour resource but, again,

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‫I want this to be as reusable as possible.

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‫All right.

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‫So, what we usually do in this constructor function

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‫is to say this.query equals the query that we got

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‫as an argument and then this.queryString

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‫is equal to the queryString.

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‫Okay?

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‫So very simple, very typical constructor function.

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‫And now, as I mentioned, I'm going to create one method

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‫for each of the functionality, starting with filter.

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‫All right.

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‫And so, let's now go ahead and cut the code from here.

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‫Or, actually, I'm going to copy it and them comment it,

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‫so that I don't do any accidental damage.

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‫So, copy and the comment

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‫and put it right here.

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‫So, a couple of things that we need to change.

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‫First on, request.query is not going to be available

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‫inside of this class.

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‫And so, that's why we actually parsed in the queryString.

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‫And so, this here is going to get replaced

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‫with this.queryString.

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‫Okay?

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‫So, again, this is just basic Javascript.

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‫Has actually nothing to do with Note or Express at all.

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‫Then the rest here is okay but this here is not okay at all.

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‫So I do not want to query the tour directly here, remember,

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‫but instead, I simply want to now add this find

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‫to the query that we already have.

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‫So this.query.find

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‫and so, that will then be this.

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‫All right?

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‫Let's, now, get rid of this.

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‫And before we add any more methods here,

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‫let's actually go ahead and use this class

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‫just so this makes more sense to you.

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‫Okay?

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‫So, how is this actually going to work?

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‫And I'm going to do it all here at the end here

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‫under Execute Query.

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‫All right?

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‫And so, what I can do now is to create a variable

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‫called Features, for example.

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‫And then from here, I will create a new API features object.

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‫Okay?

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‫So, basically, creating an instance of this API features

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‫that will then get stored into Features.

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‫And this here, we'll, then, have access to all the methods

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‫that we're going to define in the class definition.

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‫Okay?

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‫So, remember, in here, we need to pass a query

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‫and the queryString.

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‫So, the query, how do we create one?

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‫Remember, it's Tour.find.

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‫So, there's a query object and so, that's the one that

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‫we parsed into this class and then, of course,

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‫the queryString which is req.query.

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‫Okay, now, on this features here, remember,

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‫we have no access to filter.

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‫And so, let's actually put it right here afterwards.

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‫So, .filter.

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‫Give it a save.

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‫And so, just like this, we're going to run or code

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‫for the API filtering functionality.

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‫Then, here, the next line is, of course,

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‫not going to work because this query here

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‫does not anymore exist.

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‫Instead, what we have now is features.query, right?

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‫So after all this processing now, basically.

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‫Okay, so, right now, after this filter, this.query

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‫will then have this new find method on it.

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‫Okay, and so, again, this is then stored in this.query.

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‫And, later on, we will have all this other methods which,

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‫all of them, will manipulate this.query

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‫so that, in the end, this.query is the query

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‫that we want to execute.

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‫So, just like here.

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‫Okay, so, just like here, we always kept manipulating

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‫the query variable.

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‫We kept adding more and more methods to it

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‫until we, then, executed it by the end.

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‫And so, here, we're doing exactly the same.

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‫We are simply moving the code into all of these methods.

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‫Okay?

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‫Then, in the end, as I said, the query is going to be stored

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‫inside of this property here and so, yeah,

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‫that's where we, then, do the the await

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‫and get back the results.

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‫All right?

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‫Anyway, let's keep moving here and implement the sorting.

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‫So, I'm copying and commenting.

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‫So, filter and the next one is called Sort.

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‫All right.

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‫And so, here again, we need to replace request.query

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‫with this.queryString, okay.

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‫And then, query is now this.query.

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‫So let's get these four in this.query.

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‫Okay, now, the goal here is to basically

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‫chain these methods here one after another.

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‫So let me show that to you here.

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‫So we have filter and then, after that, we want to chain

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‫the sort method.

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‫Now, right now, that is not really going to work

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‫because where are we actually chaining this sort on?

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‫So, basically, we're trying to call it on the result of this

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‫but, right now, what is the result of this?

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‫Well, it's not really anything because this filter method

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‫here doesn't return anything, right?

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‫Now, this piece of code here, of course, returns

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‫the object that has just been created and so, then,

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‫we can chain the filter method on that.

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‫But the filter method, in turn, does not return anything.

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‫And so, at this point, we cannot really call a sort

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‫on the object, right?

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‫And so, the simple solution to that,

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‫and maybe you've done it earlier sometime in your code,

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‫is that we have to now return this.

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‫So, return this and this is simply the entire object, okay?

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‫And the same, then, down here.

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‫So, return this.

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‫In order to, again, return the entire object which,

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‫of course, then has access to these other methods

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‫so that we can, then, call them there.

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‫All right?

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‫So, next up is the limiting.

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‫And I'm going to call this one limitFields.

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‫And that's because all of these methods

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‫will have these verbs as names.

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‫So it's filter, sort, limit, and the paginate

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‫is going to be the next one.

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‫So, again, req.query is now this.queryString

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‫and query here is now this.query.

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‫All right?

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‫Return this and this is not correct.

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‫Okay, and finally, the pagination.

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‫Copy, comment.

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‫So, paginate.

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‫Return this and, of course, we need to

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‫replace these req.query

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‫this.queryString.

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‫And then here, just like before,

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‫it's going to be this.query.

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‫And I just realized that up there,

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‫right in the first method, we didn't do this here.

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‫So, we simply said this.query

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‫and then added the find there.

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‫But then, of course, we need to actually save it

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‫into this query property.

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‫Okay, and so, I forgot that.

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‫And we got some error here.

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‫All right, that doesn't really matter here

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‫at this moment.

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‫Or, actually, it does because this line of code here

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‫is actually in our paginate method.

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‫So let's go there.

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‫And, in fact, I actually wanted to talk to you

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‫about this here.

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‫Because, if you think about it, requesting the next page,

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‫which has zero result, is not really an error.

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‫The fact that there are no results is enough for the user

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‫to realize that, basically, the page that was requested

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‫doesn't contain any data.

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‫So we do not really need an error in this situation.

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‫And so, I'm just going to go ahead and delete all this code.

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‫Okay?

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‫So let me save it now here.

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‫And so now, of course, the error is gone.

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‫And here, we also still have to keep adding

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‫these other methods.

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‫So, limitFields and .paginate.

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‫Give it a save and, again, remember that all of this

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‫chaining here only works because after calling

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‫each of these methods, we always return this.

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‫And this is the object itself which has access

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‫to each of these methods here, making it possible

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‫to chain them just like we have it here.

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‫Okay, so, just to recap:

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‫We are creating a new object of the API features class.

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‫In there, we are parsing a query object

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‫and the query string that's coming from express.

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‫Okay?

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‫Then, in each of these four methods here that we call

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‫one after another, we, basically, manipulate the query.

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‫We keep adding more methods to it just like we've been doing

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‫up here before we did any of this refactoring, right.

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‫So, we keep adding stuff to the query here until the end,

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‫and then, by the end, we simply await the result

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‫that query so that it can come back with all the documents

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‫that were selected, okay?

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‫And that query now lives at features

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‫which is this object here.

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‫So features.query.

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‫Okay, I hope that make sense.

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‫So, before we do anything else, let's go back to Postman

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‫and actually try it out.

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‫And we can try it out right here with this Top-5-cheap route

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‫because that, actually, behind the scenes,

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‫uses all of these API features, right.

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‫So, if I send it, well, it still works.

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‫So that's fantastic.

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‫So let's close it and let me actually save it here.

245
00:12:40,490 --> 00:12:44,453
‫So, Get Top Five Cheap Tours.

246
00:12:49,220 --> 00:12:51,370
‫And yeah, I'm going to leave it there at the end.

247
00:12:51,370 --> 00:12:53,763
‫And now, just here, let's do some testing.

248
00:12:54,790 --> 00:12:58,373
‫For example, remove the sort, let me leave the limit.

249
00:12:59,570 --> 00:13:02,260
‫Difficulty, duration, price.

250
00:13:02,260 --> 00:13:04,170
‫So, I'm going to leave all of this here

251
00:13:04,170 --> 00:13:06,620
‫just to see if it still works.

252
00:13:06,620 --> 00:13:10,590
‫And it looks like everything is still working, right.

253
00:13:10,590 --> 00:13:13,110
‫So these are the exact same results that we got

254
00:13:13,110 --> 00:13:15,500
‫before our refactoring.

255
00:13:15,500 --> 00:13:17,320
‫So, great, perfect.

256
00:13:17,320 --> 00:13:20,530
‫That worked and so, let's, now, actually delete

257
00:13:20,530 --> 00:13:23,950
‫all this code from here which makes our route handler

258
00:13:23,950 --> 00:13:26,410
‫so much cleaner, doesn't it?

259
00:13:26,410 --> 00:13:30,840
‫So, that's so much better, really, it's day and night.

260
00:13:30,840 --> 00:13:31,800
‫Okay?

261
00:13:31,800 --> 00:13:34,210
‫Now, the next step is to actually go ahead

262
00:13:34,210 --> 00:13:38,500
‫and take all this code, cut it and put it into

263
00:13:38,500 --> 00:13:41,700
‫a new file, so a new module, basically.

264
00:13:41,700 --> 00:13:44,720
‫Okay, and for that, I'm going to create a new folder here

265
00:13:44,720 --> 00:13:46,563
‫which I'm going to call Utils.

266
00:13:47,420 --> 00:13:49,713
‫So that stands, basically, for utilities.

267
00:13:51,010 --> 00:13:53,850
‫And I'm going to add a couple of stuff in here

268
00:13:53,850 --> 00:13:55,503
‫over the rest of the course.

269
00:13:57,060 --> 00:13:57,893
‫Okay?

270
00:13:57,893 --> 00:14:00,050
‫So this one is going to be called

271
00:14:00,050 --> 00:14:05,050
‫APIFeatures.js and with a capital F here.

272
00:14:09,430 --> 00:14:10,263
‫All right?

273
00:14:10,263 --> 00:14:13,621
‫So, here goes our class and, in the end,

274
00:14:13,621 --> 00:14:17,823
‫we do a module.exports of this class.

275
00:14:20,040 --> 00:14:21,800
‫So, nothing new at this point.

276
00:14:21,800 --> 00:14:24,140
‫Give it a save, close it,

277
00:14:24,140 --> 00:14:27,073
‫and now, in here, we can require it.

278
00:14:28,147 --> 00:14:30,730
‫Const APIFeatures then require.

279
00:14:35,980 --> 00:14:38,490
‫Then we need to move one folder up,

280
00:14:38,490 --> 00:14:41,613
‫then into Utils and APIFeatures.

281
00:14:43,110 --> 00:14:44,210
‫Okay?

282
00:14:44,210 --> 00:14:45,313
‫One more test.

283
00:14:48,010 --> 00:14:51,000
‫And it's taking some time, and here we go.

284
00:14:51,000 --> 00:14:53,760
‫Beautiful, that's really just beautiful.

285
00:14:53,760 --> 00:14:57,720
‫Now, if we create another resource again,

286
00:14:57,720 --> 00:15:00,280
‫for example, for the users, it's going to be so easy

287
00:15:00,280 --> 00:15:02,630
‫to drop in this same functionality.

288
00:15:02,630 --> 00:15:06,110
‫All we're going to have to do is to require this file

289
00:15:06,110 --> 00:15:08,680
‫and then, basically, do the same as here.

290
00:15:08,680 --> 00:15:11,000
‫Or maybe, in that case, we don't even want

291
00:15:11,000 --> 00:15:14,040
‫to have this sorting ability or we don't want

292
00:15:14,040 --> 00:15:17,140
‫to have the filtering ability and then, all we have to do

293
00:15:17,140 --> 00:15:19,440
‫is to simply take out this line of code.

294
00:15:19,440 --> 00:15:21,680
‫And then, like magic, it'll only do

295
00:15:21,680 --> 00:15:23,280
‫these three functionalities

296
00:15:23,280 --> 00:15:25,810
‫or these three features, okay.

297
00:15:25,810 --> 00:15:27,890
‫And so, that's really great.

298
00:15:27,890 --> 00:15:29,630
‫I hope you can see the value of this

299
00:15:29,630 --> 00:15:33,353
‫and, yeah, I'm really happy with this result.