Django Rest Framework Hyperlinked Fields Understanding

Question

I can't seem to grasp the difference between HyperlinkedIdentity and HyperlinkedRelated Fields. I have a few questions that I can't seem to find the answers to online.

What is the actual difference? When would I want to use one vs. the other.

My next question is say I have 2 models, Project and Task.

A Task has a ForeignKey to Project. If I wanted the Project to hyperlink to the tasks within it, which Hyperlink field would I put in the ProjectSerializer? And what field would I put in the TaskSerializer to complement the ProjectSerializer assuming I wanted the tasks to be able to hyperlink back to the Project they are related to?

What is the difference between using the hyperlinked fields vs. just using regular nested serializers? When using hyperlinked fields, can I still filter by pk/id?

Last, What if a model had two hyperlinked relations in the serializer? From what I understand it creates a url field for each hyperlink, would it create two url fields in this case?

Thanks for any clarification you can offer, it will be a huge help towards cementing my understanding on the subject and allowing me to complete my API for my project.

Answer 1

What is the actual difference? When would I want to use one vs. the other.

HyperlinkedIdentityField is an hyperlink field for the current object itself while HyperlinkedRelatedField represent an hyperlink to other instances.

A Task has a ForeignKey to Project. If I wanted the Project to hyperlink to the tasks within it, which Hyperlink field would I put in the ProjectSerializer? And what field would I put in the TaskSerializer to complement the ProjectSerializer assuming I wanted the tasks to be able to hyperlink back to the Project they are related to?

HyperlinkedRelatedField is what you're looking for.

What is the difference between using the hyperlinked fields vs. just using regular nested serializers?

Hyperlinks can be browsed independently from the original resource. Handy if one of them belongs to another system. For example, you'll likely want to use hyperlink to tweets rather than let your server fetch them and them return them nested. Hyperlinks also allows the client to deal with its own caching rather than sending back all the data. Could be handy in case of fetching a list of items that nest the same user.

On the other hand, hyperlinks increase the network request count because it needs to fetch more data.

When using hyperlinked fields, can I still filter by pk/id?

Not sure what you mean here.

What if a model had two hyperlinked relations in the serializer? From what I understand it creates a url field for each hyperlink, would it create two url fields in this case?

Correct. hyperlinked relation are just a representation of a relation. It provides an hyperlink (an uri) to fetch the associated object.

This is useful because you won't need to know the pattern to fetch an object from the id: with a PrimaryKeyRelatedField you'll get the id but are missing the url to fetch the associated object.

This also allows the server to manage its own uri space without the need of updating the clients.

Hope this will help.