I am trying to learn django rest framework by making a simple CRUD expense tracker app. I want to add expenses from the DRF browse-able interface. All the fields required for adding the expense are not visible in the browse-able interface, which then is not allowing me to add new expense objects.
My URLs:
from django.urls import path
from rest_framework.urlpatterns import format_suffix_patterns
from expenses import views
urlpatterns = [
path('expenses/', views.ExpenseList.as_view()),
path('expenses/<int:pk>/', views.ExpenseDetail.as_view()),
path('categories/', views.CategoryList.as_view()),
path('categories/<int:pk>/', views.CategoryDetail.as_view()),
path('addexpense/', views.AddExpense.as_view())
]
urlpatterns = format_suffix_patterns(urlpatterns)
My serializers:
from rest_framework import serializers
from .models import Expense, Category
class ExpenseSerializer(serializers.ModelSerializer):
created_by = serializers.ReadOnlyField(source='created_by.username')
category = serializers.ReadOnlyField(source='category.name')
class Meta:
model = Expense
fields = ['created_by', 'amount', 'category', 'created_at', 'updated_at']
class CategorySerializer(serializers.ModelSerializer):
created_by = serializers.ReadOnlyField(source='created_by.username')
class Meta:
model = Category
fields = ['created_by', 'name', 'description', 'created_at', 'updated_at']
My models:
from django.db import models
# Create your models here.
class Category(models.Model):
created_by = models.ForeignKey('auth.User', related_name='category', on_delete=models.CASCADE)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
name = models.CharField(max_length=256, null=False, blank=False)
description = models.CharField(max_length=256, null=False, blank=False)
# maybe add bill photo option here
class Expense(models.Model):
created_by = models.ForeignKey('auth.User', related_name='expense', on_delete=models.CASCADE)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
category = models.ForeignKey(Category, on_delete=models.CASCADE, null=False, blank=False)
amount = models.DecimalField(decimal_places=2, null=False, blank=False, default=0.00, max_digits=10)
And my views:
from django.shortcuts import render
from expenses.models import Category, Expense
from expenses.serializers import CategorySerializer, ExpenseSerializer
from rest_framework import generics
from rest_framework import permissions
from .permissions import IsOwnerOrReadOnly
# Create your views here.
class ExpenseList(generics.ListAPIView):
queryset = Expense.objects.all()
serializer_class = ExpenseSerializer
class AddExpense(generics.CreateAPIView):
permission_classes = [permissions.IsAuthenticated]
queryset = Expense.objects.all()
serializer_class = ExpenseSerializer
def perform_create(self, serializer):
serializer.save()
class ExpenseDetail(generics.RetrieveUpdateDestroyAPIView):
permission_classes = [permissions.IsAuthenticated]
queryset = Expense.objects.all()
serializer_class = ExpenseSerializer
class CategoryList(generics.ListCreateAPIView):
permission_classes = [permissions.IsAuthenticated]
queryset = Category.objects.all()
serializer_class = CategorySerializer
def perform_create(self, serializer):
serializer.save(created_by=self.request.user)
class CategoryDetail(generics.RetrieveUpdateDestroyAPIView):
permission_classes = [permissions.IsAuthenticated]
queryset = Category.objects.all()
serializer_class = CategorySerializer
This is what I see on the addexpense page right now:
As you can see, I don't see an option to add a category related to the expense.
On trying to add an expense, I get the error message:
Environment:
Request Method: POST
Request URL: http://127.0.0.1:8000/addexpense/
Django Version: 4.0.5
Python Version: 3.10.6
Installed Applications:
['django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'rest_framework',
'expenses']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware']
Traceback (most recent call last):
File "/usr/local/lib/python3.10/dist-packages/django/db/backends/utils.py", line 89, in _execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.10/dist-packages/django/db/backends/sqlite3/base.py", line 477, in execute
return Database.Cursor.execute(self, query, params)
The above exception (NOT NULL constraint failed: expenses_expense.created_by_id) was the direct cause of the following exception:
File "/usr/local/lib/python3.10/dist-packages/django/core/handlers/exception.py", line 55, in inner
response = get_response(request)
File "/usr/local/lib/python3.10/dist-packages/django/core/handlers/base.py", line 197, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python3.10/dist-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
return view_func(*args, **kwargs)
File "/usr/local/lib/python3.10/dist-packages/django/views/generic/base.py", line 84, in view
return self.dispatch(request, *args, **kwargs)
File "/home/praxmon/.local/lib/python3.10/site-packages/rest_framework/views.py", line 509, in dispatch
response = self.handle_exception(exc)
File "/home/praxmon/.local/lib/python3.10/site-packages/rest_framework/views.py", line 469, in handle_exception
self.raise_uncaught_exception(exc)
File "/home/praxmon/.local/lib/python3.10/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
raise exc
File "/home/praxmon/.local/lib/python3.10/site-packages/rest_framework/views.py", line 506, in dispatch
response = handler(request, *args, **kwargs)
File "/home/praxmon/.local/lib/python3.10/site-packages/rest_framework/generics.py", line 190, in post
return self.create(request, *args, **kwargs)
File "/home/praxmon/.local/lib/python3.10/site-packages/rest_framework/mixins.py", line 19, in create
self.perform_create(serializer)
File "/home/praxmon/code/expensetracker/expenses/views.py", line 23, in perform_create
serializer.save()
File "/home/praxmon/.local/lib/python3.10/site-packages/rest_framework/serializers.py", line 212, in save
self.instance = self.create(validated_data)
File "/home/praxmon/.local/lib/python3.10/site-packages/rest_framework/serializers.py", line 962, in create
instance = ModelClass._default_manager.create(**validated_data)
File "/usr/local/lib/python3.10/dist-packages/django/db/models/manager.py", line 85, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/usr/local/lib/python3.10/dist-packages/django/db/models/query.py", line 514, in create
obj.save(force_insert=True, using=self.db)
File "/usr/local/lib/python3.10/dist-packages/django/db/models/base.py", line 806, in save
self.save_base(
File "/usr/local/lib/python3.10/dist-packages/django/db/models/base.py", line 857, in save_base
updated = self._save_table(
File "/usr/local/lib/python3.10/dist-packages/django/db/models/base.py", line 1000, in _save_table
results = self._do_insert(
File "/usr/local/lib/python3.10/dist-packages/django/db/models/base.py", line 1041, in _do_insert
return manager._insert(
File "/usr/local/lib/python3.10/dist-packages/django/db/models/manager.py", line 85, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/usr/local/lib/python3.10/dist-packages/django/db/models/query.py", line 1434, in _insert
return query.get_compiler(using=using).execute_sql(returning_fields)
File "/usr/local/lib/python3.10/dist-packages/django/db/models/sql/compiler.py", line 1621, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python3.10/dist-packages/django/db/backends/utils.py", line 103, in execute
return super().execute(sql, params)
File "/usr/local/lib/python3.10/dist-packages/django/db/backends/utils.py", line 67, in execute
return self._execute_with_wrappers(
File "/usr/local/lib/python3.10/dist-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/usr/local/lib/python3.10/dist-packages/django/db/backends/utils.py", line 84, in _execute
with self.db.wrap_database_errors:
File "/usr/local/lib/python3.10/dist-packages/django/db/utils.py", line 91, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/usr/local/lib/python3.10/dist-packages/django/db/backends/utils.py", line 89, in _execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.10/dist-packages/django/db/backends/sqlite3/base.py", line 477, in execute
return Database.Cursor.execute(self, query, params)
Exception Type: IntegrityError at /addexpense/
Exception Value: NOT NULL constraint failed: expenses_expense.created_by_id
My question: Why are all the fields not visible on this page? How do I add them? Is there something wrong with my serializer?
CodePudding user response：
Try this:
created_by = serializers.CharField(source='created_by.username', read_only=True)
category = serializers.CharField(source='category.name', read_only=True)
CodePudding user response：
There are a few things that I noticed.
Firstly, you "don't see an option to add a category related to the expense."
However if you go to your ExpenseSerializer you will see that you have set the category field to be a ReadOnlyField. If you remove that line, you should be able to set the ID of the category that you want and it should work.
class ExpenseSerializer(serializers.ModelSerializer):
created_by = serializers.ReadOnlyField(source='created_by.username')
category = serializers.ReadOnlyField(source='category.name')
class Meta:
model = Expense
fields = ['created_by', 'amount', 'category', 'created_at', 'updated_at']
Secondly, the error you are receiving has nothing to do with the category but has to do with the creation of your Expense object.
At the very end it says:
Exception Type: IntegrityError at /addexpense/
Exception Value: NOT NULL constraint failed: expenses_expense.created_by_id
So what is happening is that you are trying to create an expense but you haven't set the created_by field. This might be because your AddExpense view doesn't really do anything with it's perform_create function. (You aren't setting the user like you do in the perform_create of CategoryList)