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‫In this video,

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‫we're gonna be building a handler factory function

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‫in order to delete review documents,

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‫but also documents from all the other collections,

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‫all with one simple function.

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‫So, as I mentioned right at the beginning of this section,

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‫adding very similar handlers to all of our controllers

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‫will create a lot of duplicate code, right?

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‫Because all these update handlers,

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‫or all these delete handlers,

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‫or all these create handlers,

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‫they really all just look basically the same, right?

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‫Also, imagine that we wanted to change

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‫like some https status code or status message.

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‫Then we would have to go into each and every controller

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‫and then change all the handlers in there.

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‫And so, instead of manually writing all these handlers,

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‫why not simply create a factory function

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‫that's gonna return these handlers for us?

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‫So, a factory function is exactly that.

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‫It's a function that returns another function,

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‫and in this case our handler function.

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‫So, for deleting, for creating, for updating,

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‫and also for reading resources.

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‫Okay and I know that this whole concept can be a bit complex

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‫to wrap your head around,

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‫and that's the reason why I left this

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‫for the later part of this course.

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‫But now, I believe that you're actually ready

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‫to implement this kinda stuff.

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‫So this kind of logic is what every advanced

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‫JavaScript developer should be able to implement,

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‫and so again I believe that at this point in the course

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‫you're really ready to start using advanced concept

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‫like this, all right.

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‫But enough talk, let me now show you how it actually works

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‫by using the delete handler as a first example.

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‫And so actually we have one in the tour controller,

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‫and so let's go ahead and copy that one,

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‫so delete tour.

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‫Okay, so I copied it basically

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‫as a template for us to follow.

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‫So let's create a new file, and I'm going to do that

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‫in the controllers.

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‫All right,

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‫so handler...

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‫factory.js.

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‫And I'm doing this is the controllers folder,

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‫well because the functions that we're gonna write here

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‫will basically return controllers.

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‫And so for me it makes a lot of sense

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‫that you put them here.

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‫So let's just copy this part here,

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‫just to keep it as a reference.

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‫So again the goal here is to basically create a function,

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‫which will then return a function

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‫that looks like this one here.

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‫But of course not only for the tour,

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‫but for every single model that we have in our application

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‫and that we might have in the future.

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‫So this function needs to be prepared for that,

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‫and so what that means is that inside the factory function,

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‫we will pass in the model, all right.

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‫So let's call this one deleteOne.

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‫And it's called like this, again,

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‫because this function is not only going

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‫to work to delete tours,

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‫but also to delete reviews and users

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‫and in the future some other documents

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‫that we might also have.

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‫So as I was saying in the beginning,

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‫we will pass the model into this function.

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‫So we pass the model and then we create a new function,

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‫and that function will right away

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‫then return our async function,

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‫so basically all of this or async handler function.

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‫Okay, and so now all we need to do is to actually change

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‫from the specific tool model to the more generic model.

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‫Then here we will also change this from tour to the document

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‫because again, we will not know what kinda document is this.

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‫So this function will not really know if it is a tour,

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‫or if it is a review, or a user.

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‫And so we need to take the tour out of all of this,

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‫and that's actually it.

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‫So this basically the generalization

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‫of this specific function, which worked only for tours,

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‫and now this new one works for every model.

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‫What we also need to do here is to import this catchAsync

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‫and also this AppError.

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‫So catchAsync...

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‫and I believe it's in the utilities folder.

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‫And then, not AppError but catchAsync.

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‫Then duplicate this here,

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‫AppError, and this here is uppercase.

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‫Give it a save, and we're now ready

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‫to actually test this out.

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‫So this is how it's going to work,

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‫first of all we need to import that handler factory.

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‫And so let's say,

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‫and I'm simply going to call it factory here.

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‫So require, and it's in the same folder,

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‫so handler factory.

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‫All right and so let's comment this one here out,

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‫or actually not all of this.

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‫Yeah or actually we can comment it out,

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‫and so the new exports.deletes tour will be...

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‫factory.deleteOne and then pass in the model,

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‫which is tour.

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‫And that's it, that's all we need to do.

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‫So just to recap very quickly here,

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‫so we call this deleteOne function,

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‫then in there we pass the model,

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‫and so what's going to happen is that this function

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‫will then right away return this handler function

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‫that we had before.

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‫Simply the specific model, which before was the tour,

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‫is now going to be replaced with the one

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‫that we passed into the function.

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‫And by the way this works because of JavaScript closures,

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‫which is just a fancy way of saying

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‫that this inner function here will get access

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‫to the variables of the outer function

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‫even after the outer has already returned.

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‫So calling this function here

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‫will then return another function,

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‫which will then sit here and wait until it is finally called

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‫as soon as we hit the corresponding route.

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‫And so let's now try exactly that.

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‫So delete tour,

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‫okay, and let's choose a tour

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‫that we don't really need here for now.

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‫So let's say...

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‫now let's say here The Snow Adventurer

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‫'cause it also doesn't have any reviews.

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‫So let's send that,

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‫oh and now we don't have permission to preform the action,

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‫and that's because we're not logged in as an admin.

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‫So let's try that,

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‫and so this is the admin that we need to be logged in.

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‫Okay, so that's done.

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‫And so now this should work, and indeed it did work.

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‫And so that's proof that our factory function

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‫is really doing it's job.

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‫Okay 'cause if you now come back here,

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‫we had 10 results and so now we should only get nine,

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‫so perfect.

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‫And now the goal is to be able to use this

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‫in each and every single controller.

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‫So let's copy this here

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‫and go to the reviews.

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‫Oh and of course we need it up here,

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‫right in the beginning, now right,

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‫and so now export.deleteReview

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‫is equal to factory.deleteOne

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‫with the review model.

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‫And that's it, that's all we need to do

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‫in order to implement the delete handler.

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‫Now of course we also need to specify the route handler.

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‫Now of course we need to specify the route itself,

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‫and so let's do that here as well.

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‫So router.route

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‫because here we actually need the ID parameter.

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‫And now delete is simply reviewController.deleteReview,

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‫and I'm not messing with the permission here,

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‫neither with authentication

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‫because for now I just want to make this work

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‫and worry about that stuff a bit later in this section.

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‫Okay, so let's close this stuff up here.

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‫So get all reviews,

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‫all right,

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‫let's save this and this one as well.

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‫So that now we can start with a blank sheet here

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‫and let's just start by getting all reviews,

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‫so that we can now delete one.

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‫And so let's delete, well just this one.

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‫Okay, now we also need of course this,

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‫and then the delete http method.

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‫We need no authorization at this point,

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‫so let's just send it.

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‫And indeed no content, so 204.

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‫And if we now get all the reviews,

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‫then we should be back to having just three.

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‫Yep, that works and so let's move on to the next one.

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‫Okay so reviews, reviews.

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‫Let's get this line of code here and now finally add it

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‫to the user controller as well.

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‫All right, and of course all of this,

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‫I understand it's a bit confusing now messing

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‫with all of these different files,

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‫but we just need to do it once and then we're done

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‫with all that confusion.

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‫So here we already had the export.deleteUser,

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‫now all we need to do is to then call our factory function,

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‫so deleteOne and then the user.

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‫Now only the administrator should later be able

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‫to actually delete users because remember that

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‫when the user deletes himself,

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‫then they will not actually get deleted

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‫but only active will be set to false.

200
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‫But the administrator on the other hand

201
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‫is really gonna be able to delete the user effectively

202
00:11:25,710 --> 00:11:26,940
‫from the database.

203
00:11:26,940 --> 00:11:28,550
‫But again, we're going to worry

204
00:11:28,550 --> 00:11:31,023
‫about that permission stuff a bit later.

205
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‫For now, let's check in the userRoutes

206
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‫if the route is actually implemented,

207
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‫and yeah it is down here.

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‫And so since we now implemented this,

209
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‫let's also test it here again also on Postman.

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‫So first let's save this one.

211
00:11:54,440 --> 00:11:55,360
‫So...

212
00:11:56,210 --> 00:11:59,373
‫delete review,

213
00:12:02,000 --> 00:12:07,000
‫and now let's simply copy this

214
00:12:08,420 --> 00:12:10,910
‫into yet another route.

215
00:12:10,910 --> 00:12:13,063
‫So delete and then one user,

216
00:12:14,340 --> 00:12:16,690
‫but I'm actually not really going to do it now.

217
00:12:17,970 --> 00:12:22,253
‫All I want is to just get some random ID.

218
00:12:23,350 --> 00:12:26,703
‫Or actually let's just create a new user,

219
00:12:27,780 --> 00:12:31,323
‫so basically sign up, and then delete that one right away.

220
00:12:32,500 --> 00:12:35,563
‫So hello, like this.

221
00:12:38,690 --> 00:12:43,360
‫Get all users, and then it's this guy here.

222
00:12:43,360 --> 00:12:46,963
‫And so let's delete him right away,

223
00:12:48,310 --> 00:12:51,560
‫so we send, we get 204 no content.

224
00:12:51,560 --> 00:12:53,833
‫And of course, now he should be gone.

225
00:12:54,840 --> 00:12:56,740
‫Now if we try to see her again,

226
00:12:56,740 --> 00:12:58,680
‫so basically trying to delete a user

227
00:12:58,680 --> 00:13:01,320
‫that is no longer there, we should get an error.

228
00:13:01,320 --> 00:13:04,673
‫So let's take a look, and indeed no document found

229
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‫with that ID.

230
00:13:06,330 --> 00:13:09,203
‫And so this means that in our factory function,

231
00:13:10,570 --> 00:13:15,550
‫so right here, all of this the AppError and the catchAsync,

232
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‫all of that is still intact.

233
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‫So everything still works just the same as before.

234
00:13:20,490 --> 00:13:23,283
‫Now so that was also important to test here.

235
00:13:25,670 --> 00:13:27,860
‫Let's just quickly save this here as well,

236
00:13:27,860 --> 00:13:31,660
‫so each and every single endpoint that we're implementing,

237
00:13:31,660 --> 00:13:33,810
‫I'm also adding it here into Postman

238
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‫because a bit later we will then actually be able

239
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‫to actually create some API documentation

240
00:13:39,420 --> 00:13:43,970
‫based on all of this that we have saved here in Postman.

241
00:13:43,970 --> 00:13:47,713
‫So that's yet another handy feature of this application.

242
00:13:50,253 --> 00:13:51,960
‫So we have delete the current user,

243
00:13:51,960 --> 00:13:54,520
‫and again that's different from just deleting the user

244
00:13:54,520 --> 00:13:56,800
‫because this one here is for administration

245
00:13:56,800 --> 00:13:59,803
‫and this one is for the currently logged in user,

246
00:14:00,820 --> 00:14:01,963
‫so very different.

247
00:14:03,320 --> 00:14:06,750
‫Okay, so this was our first factory function

248
00:14:06,750 --> 00:14:09,660
‫only for deleting and only for you to understand

249
00:14:09,660 --> 00:14:11,290
‫the concept itself.

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‫Next up, we're then gonna implement factory functions

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‫for updating and for creating documents.