Django Queries

[thorny niche]

Hi,

I need ideas on how to handle this logic. I have 2 models: Albums and Photos. The Photos model is related to the Albums model by a ForeignKey. Now, it could happen that I have multiple albums and multiples photos in each Album. How can I define this in the views such that only photos in each album is displayed rather than all photos in all albums? I am a bit confused on how to go about it. Thanks.

PS: This is in Django

[cedar fog]

The url should identify which album to use via a URL parameter. Check out the docs on url dispatching.

Once you're passing that album identifier (can be ID, a slug or some other unique characteristic), you can now filter the photos by that album.

The official django tutorial covers something similar I think.

[glad citrus]

@thorny niche I didn't understand what you need?

{
  album1: [photo1, photo2],
  album2: [photo3, photo4]
}

did you find it out

[thorny niche]

I need a view that only displays photos one album at a time, not all photos in all albums. What I mean is once a visitor clicks on an album, the photos in it should be on display.

[thorny niche]

Not the solution.

[glad citrus]

like Tim said, you pass the album id/slug parameter in url

do you have a separate frontend or you use django templates?

def get_album_photos(request, id):
  photos = Photo.objects.filter(album__id=id)
  ... get whatever you need

# urls

path("albums/<int:id>/photos/", get_album_photos)

something like this

[cedar fog]

https://docs.djangoproject.com/en/4.1/intro/tutorial04/ this part of the tutorial shows how you can show results and votes for a particular question. An album in your data model is the equivalent to a question in the tutorial's example.

[thorny niche]

I have separate frontend.

[glad citrus]

the same logic applies

make an api call with album id/slug

then get photos for that album

which is what Tim said, why do you say not the solution?

[thorny niche]

I think the solution should be strictly in the views...

[thorny niche]

Okay. I will look at your response again and read the article too.

[glad citrus]

this is a view?

[thorny niche]

Looks like it. Can this be used in APIView in Django REST framework?

[glad citrus]

class AlbumsView(APIView):
  def get(self, request):
    albums = Album.objects.all()
    serializer = YourAlbumSerializer
    return Response(serializer.data)


class AlbumsPhotosView(APIView):
  def get(self, request, album_id=None):
    photos = Photo.objects.filter(album__id=album_id)
    serializer = YourPhotosSerializer
    return Response(serializer.data)

class based view or function, doesnt matter

[thorny niche]

Ah! This seems right. Thanks a lot.

[thorny niche]

Okay. One more thing please...how would permission be handled in this view such that only authenticated users can perform CRUD operations on albums and photos, and unauthenticated users can only read...?

[glad citrus]

you are using DRF right?

from rest_framework.permissions import IsAuthenticated, DjangoModelPermissions

class YourView(...):
  permission_classes = [IsAuthenticated, DjangoModelPermissions, your, other, permissions]

https://www.django-rest-framework.org/api-guide/permissions/#djangomodelpermissions

using DjangoModelPermissions will use django's built in crud permissions for lookup

[thorny niche]

Yes, I am.

[glad citrus]

if most of your site requires authentication, it's always better to set base permission to IsAuthenticated in your settings

[thorny niche]

And thank you for the resource.

[glad citrus]

then you just use AllowAny permission on the views that doesn't require authentication

[thorny niche]

Okay.

[thorny niche]

If I set base authentication to IsAuthenticated, does this mean I wouldn't need to explicitly state it in the views and then for views that do not require permissions, I can explicitly use AllowAny?

[glad citrus]

yes

https://www.django-rest-framework.org/api-guide/settings/#default_permission_classes

here

[thorny niche]

Okay. which authentication framework or library would you suggestion? I tried Djoser but I do not understand how it works. Plus, I also need to use Djoser alongside a token authentication like JWT. How can I combine both?

[thorny niche]

Okay. Thank you so much.

[glad citrus]

if you want to implement social auth in future

i think it was django-allauth?

better look it up, can't say for sure

[thorny niche]

Alright then. I will.

[thorny niche]

In reference to this, in the same vein, if I want to define a post request, I would define it where I want to under the APIView?

[glad citrus]

yes, you define request methods under the class based view @thorny niche

post/get/patch/put/delete..

look at GenericAPIView if you are working with models in a view (this is the case most of the time)

[thorny niche]

Which means if I wish to perform these operations, I have to define each of the 4 operations in the views?

[glad citrus]

yes, otherwise you will get method not allowed error

[thorny niche]

Does it allow for custom definition of the operations as well?

[glad citrus]

yes, but it will ask you to set get_queryset method

[thorny niche]

You have explained better than even the documentation. It's clear to me. Thank you.

[glad citrus]

or queryset attribute for the class

[thorny niche]

Hmm...Okay. I will look it up if that's the case.

[glad citrus]

https://www.django-rest-framework.org/api-guide/generic-views/#generic-views better look here about generic views, I personally always use GenericView and define post/patch/delete/get methods but maybe you don't have to do that

[thorny niche]

I really appreciate the time you have taken, but I have one more question as regards serializers. I read that they are a sort of replacement for forms in DRF. This means we will need to process the serializer when we want to use it in a view?

[glad citrus]

@thorny niche I would say yes and no. Serializer basically serializes your data json to python and vice-versa. But obviously it has many benefits like validation, custom validation, custom crud operations, representation of nested relations etc etc

but also comes with drawbacks

[thorny niche]

Hmmm....would you say the drawbacks should make one avoid using them? A friend mentioned that serializers aren't very efficient and should be avoided or something. Didn't give an alternative so I didn't believe him.

[glad citrus]

yes when you have 100 rows, 1000 rows of data, it seems all fine. when you have lots of data you start to notice the drawbacks (slow)

there are ways to improve performance, for example ModelSerializer is slow compared to base serializer serializers.Serializer because it has extra logic related to model

when you have a model

class User(Model):
  name
  full_name
  email
  age
  city
  ...

class UserSerializer(serializers.ModelSerializer):
  class Meta:
    model = User
    fields = "__all__"

If I wanted to serialize User data, unless you have some advanced field calculations, I don't see the need to use serializer.

you could just do User.objects.values()

the speed difference is very noticable

but for create/update, I would use serializer because It's easier to implement custom validations and provides abstraction

you can read https://hakibenita.com/django-rest-framework-slow

very good article regarding this topic

In late 2013, Tom Christie, the creator of Django Rest Framework, wrote an article discussing some of DRF's drawbacks. In his benchmarks, serialization accounted for 12% of the total time spend on processing a single request. In the summary, Tom recommends to not always resort to serialization:

4. You don't always need to use serializers.

For performance critical views you might consider dropping the serializers entirely and simply use .values() in your database queries.

[thorny niche]

Oh, thank you so much for this. I really appreciate your help.

[glad citrus]

you are welcome