django tastypie only fetch a particular field of a particular object

Question

In tastypie my url: /api/v1/course/1/?format=json gives the following json:

{
created_on: "2012-02-27T08:00:54",
description: "this is course 1",
id: "1",
resource_uri: "/api/v1/course/1/",
subjects: [
    "/api/v1/subject/1/",
    "/api/v1/subject/2/"
],
title: "Course 1"
}

I want to do something like:

/api/v1/course/1/subjects/?format=json   

to get only the list of subjects for a given course. Is this possible?

Bostwick

as json services does not require SEO I don't get the point. Or maybe you want all subjects related to you course. – Legislative

django-tastypie.readthedocs.org/en/latest/… – Legislative

yes, I just was wondering if in a more complicated nested json, can i just query for the entity I want. I just want the subjects, if possible. In reality this json is too big and I was thinking if there is a way to do this without writing a new resource. – Bostwick

Answer 1

I'm guessing you want to do something like this where you specify a fields parameter so users can request only the fields they want. In your case, a user would send the request

/api/v1/course/1/?format=json&fields=subjects 

One way to implement this is to extend Tastypie to give you this functionality. Currently, the full_dehydrate method iterates over all fields and dehydrates each of them. You can add in a check to see if the user entered fields and if so, just skip the dehydrate phase for any fields that were not specified.

Crosshatch

Here is an extension that does just that: github.com/dan-klasson/django-tastypie-specified-fields. Although it does not yet support m2m. – Wendywendye

Answer 2

The reverse relations are not created by default in tastypie but it looks pretty simple:

http://django-tastypie.readthedocs.org/en/latest/resources.html#reverse-relationships

class CourseResource(ModelResource):
    subjects = fields.ToManyField('myapp.api.resources.SubjectResource', 'subjects', full=True)
    class Meta:
        queryset = Course.objects.all()

class SubjectResource(ModelResource):
    course = fields.ToOneField(CourseResource, 'courses')

    class Meta:
        queryset = Subject.objects.all()

Legislative

No, I have done this exact same thing which shows subjects within the course json, as per the json posted in the question. I was wondering if I can just get the subjects only, or does my question not make sense? thanks. – Bostwick

I added full=True, it's no more links but full objects... was it what you wanted? I'm discovering tastypie with you to answer so please be indulgent ^^. – Legislative

you still may do 2 course ressource to have one with only subjects our have a subject ressource with a custom query_filter django-tastypie.readthedocs.org/en/latest/… – Legislative

Answer 3

I had the same issue. I then implemented a very simple django-tastypie extension called django-tastypie-specific-fields which will help you to select the fields you are interested in. You will able to fetch your data with such a simple request

/api/v1/course/1/?format=json&fields=subjects

It will also give you much more possibilities.

Christianachristiane