There is one more thing I need to do to make sure the API doesn't have to parse

thousands of reviews in a single API request, pagination.

Rest framework provides some built in pagination that will work automatically

with generic views and view sets.

You implement a global default by setting the default pagination in

the settings file.

If you need to, you can get very explicit and

set pagination directly on your view sets or generic views.

All right, so I think it's probably a good idea to set up the default pagination

first and that gets done in settings.py.

So you remember down, way way down here at the bottom, so much scrolling,

there is this rest framework dictionary where I've set all of my arguments.

So I'm gonna add a new one here which is default pagination,

pagination_class and notice this is class not classes.

You only get one default pagination class.

There's not like a fallback.

So rest_framework.pagination.PageNumberPagin-

ation.

And that's just a little over 80, so I'm gonna break it.

Nah, I'll leave it, I don't care.

All right, and then page size.

Which is how many items are on a page.

I'm going to set that to five.

Some of you may have been shocked by me saying, I don't care, yeah just welcome to

my world where sometimes it just doesn't matter if it's a little over 80.

All right, so the first one of these sets the pagination class,

which is the class that's going to be used to figure out how to break things into

chunks of a particular size.

So into pages and

then the page size says how many things are going to be on each particular size.

Okay? I'm using

a small number cuz I don't have a lot of stuff in my database here.

You would probably use something like 10, or 50, or 100 on your own stuff.

So just keep that in mind.

So, I'll refresh this, and the content here has now changed.

So instead of it just being a list of all these items,

we now have the list of the items inside a key called results.

We have a count, which is how many things there are.

And we have next and previous, which would be URLs to the next and

previous pages of results.

I can show you that real quick by changing this, to one.

Refresh, there we go, and my next page would be here at page two.

And if we go to page two then I have a next page at page three and

I have a previous page at slash courses and

you can also assume this had a question mark page equals one.

So kinda cool, kinda nice.

I'm gonna put that back to five.

All right so that's fairly straightforward and handy.

Now the default pagination gets applied to all generic views and

view sets and all that kind of stuff in the project.

So, just keep in mind any changes you make to the default pagination

potentially will affect all of the pages of your API.

The default pagination won't automatically work on your ad hoc views,

so like this, let me get to it,

this reviews view that we gave here, this detail route that won't get paginated.

You'll have to make your own calls to the paginator to handle that.

Since I don't have a lot of reviews yet,

I'm also going to change the pagination size on this one to one.

Let's let's see how to do this custom pagination.

So inside here we have all of our normal stuff.

Nothing has changed yet.

So here I'm gonna do self.pagination_class.page_size

is gonna be equal to one.

So this pagination class was set by that setting that I set awhile ago.

The view knows what the pagination class is and what its page size is.

By default the page size is five.

I'm setting that to be one.

So now I want to do reviews equals model.Review.objects.filter.

Course_id = pk, so get all the reviews for

the current course and then I'm gonna

do page = self.paginate_querryset,

that's what it is, reviews.

If page is not None, so so long as I have a page.

Serializer equals serializers.reviewSerializer page and

many is equal to true because it's probably more

than one thing on there, right?

And then I'll return self.get_paginated_response.

Wow, some days, serializer.data and otherwise,

if that somehow falls through, then serializer = serializers.

Yeah, that's what I want to do right there.

Serializer = Serializers.ReviewSerializer, and I want to give it reviews,

and many=True,

because we've got all of those reviews coming through.

All right, so I changed it a little bit.

So let's go through what I did here.

So I set the paginater to have a page size of one.

Because I want just one item on a page.

I want to grab all the reviews and I'm going to paginate that query set.

Assuming that I have some pages then I'm gonna send this out through.

If, somehow, I don't have like pages or whatever, then I'm just going to

serialize all the reviews that I do have and I'm going to return a response.

So now let's try going to one slash reviews,

and if I look, I still have count next previous and results right,

because the reviews are now being paginated just like the courses were.

So that's cool.

There is more than one option and style for pagination rest framework.

You should, you know, check out your options, you get to know them all.

So check the teacher's notes and

you'll find a link to the pagination documentation right down there.

Pagination is a great way to reduce the amount of strain on your A.P.I.

due to large records or lots of related records.

At this point you have a strong customizable A.P.I., that's easy for

users to get the data they need.

Now, though, it's time to think about securing this A.P.I.

because the wild internet isn't nearly as nice as I wish it was.