How will I serialize complex Django Models to json?

Question

I am trying to create a REST service in my django application using djangoRestframework django-rest.

I have model Student in MyModels.py which is has follows,

from django.db import models

class Student(object) :
    def __init__(self,first_name,middle_name,last_name,subject_list=None):
            self.first_name = first_name
            self.last_name = last_name
            self.middle_name = middle_name
            self.subject_list = subject_list

class Subject(object) :
    def __init__(self,name):
            self.name = name

The below code is from views.py

def getStudentList(request):
my_list = []
my_list.append(Student(first_name="Alajandro",middle_name="Santana",last_name="Gonzales"))
my_list.append(Student(first_name="Timothy",middle_name="Carlos",last_name="Robins"))
my_list.append(Student(first_name="Nathan",middle_name="Nick",last_name="Mathews"))
my_list.append(Student(first_name="John",middle_name="Nelson",last_name="Kennedy"))
my_list.append(Student(first_name="Tom",middle_name="Kenny",last_name="Cruise"))
my_list.append(Student(first_name="Jerry",middle_name="Sanvile",last_name="McGuire"))
my_list.append(Student(first_name="Jason",middle_name="San",last_name="Statham"))

student_list = []

for student in my_list:
    student_ser = rest.StudentSerialize(student)
    student_list.append(student_ser.data.copy())

json = JSONRenderer().render(student_list)
return HttpResponse(json)

The url mapping in urls.py is

 url(r'^studentList/', views.getStudentList),

The response is get from URL http://127.0.0.1:8083/studentList/

is

[{"first_name":"Alajandro","middle_name":"Santana","last_name":"Gonzales"},{"first_name":"Timothy","middle_name":"Carlos","last_name":"Robins"},{"first_name":"Nathan","middle_name":"Nick","last_name":"Mathews"},{"first_name":"John","middle_name":"Nelson","last_name":"Kennedy"},{"first_name":"Tom","middle_name":"Kenny","last_name":"Cruise"},{"first_name":"Jerry","middle_name":"Sanvile","last_name":"McGuire"},{"first_name":"Jason","middle_name":"San","last_name":"Statham"}]

Now If I am interested in also passing subjects in the json. I am trying to do is one-to-many relationship between student and subjects. i.e one student can have many subjects.

So i am expecting this json as an output

 [{
      "name" : "Tom",
      "subject_list" : [{..},{},{},....]
  },{},{}...]

For this above I have done following changes in code

my MyModel.py file

from django.db import models

class Student(object) :

    def __init__(self,first_name,middle_name,last_name,subject_list=None):
            self.first_name = first_name
            self.last_name = last_name
            self.middle_name = middle_name
            if subject_list is None:
                    self.subject_list = subject_list

class Subject(object) :
    def __init__(self,name):
            self.name = name

My MyREST.py contains

from MyModels import Student
from MyModels import Subject
from rest_framework import serializers


class StudentSerialize(serializers.Serializer):
    first_name = serializers.CharField(max_length=200)
    middle_name = serializers.CharField(max_length=200)
    last_name = serializers.CharField(max_length=200)

My views.py contains

def get_student_list(request):

my_list = []
my_list.append(Student(first_name="Alajandro",middle_name="Santana",last_name="Gonzales"))
my_list.append(Student(first_name="Timothy",middle_name="Carlos",last_name="Robins"))
my_list.append(Student(first_name="Nathan",middle_name="Nick",last_name="Mathews"))
my_list.append(Student(first_name="John",middle_name="Nelson",last_name="Kennedy"))


subject_list = []
subject_list.append(Subject(name="Computer Science"))
subject_list.append(Subject(name="Physics"))
subject_list.append(Subject(name="Chemistry"))

my_list.append(Student(first_name="Jason",middle_name="San",last_name="Statham",subject_list=subject_list))
my_list.append(Student(first_name="Tom",middle_name="Kenny",last_name="Cruise",subject_list=subject_list))
my_list.append(Student(first_name="Jerry",middle_name="Sanvile",last_name="McGuire",subject_list=subject_list))

student_list = []
for student in my_list:
    student_ser = rest.StudentSerialize(student)
    student_list.append(student_ser.data.copy())


json = JSONRenderer().render(student_list)
return HttpResponse(json)

And in urls.py I added

 url(r'^student_list/', views.get_student_list),

Now If I hit the URL I still get json output as

[{"first_name":"Alajandro","middle_name":"Santana","last_name":"Gonzales"},{"first_name":"Timothy","middle_name":"Carlos","last_name":"Robins"},{"first_name":"Nathan","middle_name":"Nick","last_name":"Mathews"},{"first_name":"John","middle_name":"Nelson","last_name":"Kennedy"},{"first_name":"Jason","middle_name":"San","last_name":"Statham"},{"first_name":"Tom","middle_name":"Kenny","last_name":"Cruise"},{"first_name":"Jerry","middle_name":"Sanvile","last_name":"McGuire"}]

But I don't get the subjects.

What I should add in class SudentSerialize so that if I set subject_list in object of student, I will get json of Student an the property subject_list will have subject json array.

Answer 1

You have to use nested Relationships to do this job :

Here is an example :

class SubjectSerializer(serializers.Serializer):
    name = serializers.CharField(max_length=200)

    class Meta:
        fields = [
            'name',
        ]

class StudentSerializer(serializers.Serializer):
    first_name = serializers.CharField(max_length=200)
    middle_name = serializers.CharField(max_length=200)
    last_name = serializers.CharField(max_length=200)
    # nested relationship
    subjects = SubjectSerializer(many=True)

    class Meta:
        fields = [
            'first_name',
            'last_name',
            'middle_name',
            'subjects'
        ]

Read Django Rest Framework - Nested relationships for more information

Answer 2

You are looking for nested serializers. The documentation should cover everything you need to know about this.

Please also take some time to run the 6 steps of the tutorial. It will give you hints about how to use DRF.