How to update some data when post object in Django Rest? - django

Question

I have this Serializer:
class LikeSerializer(serializers.ModelSerializer):
user = serializers.PrimaryKeyRelatedField(queryset=ExtUser.objects.all(), required=False, allow_null=True, default=None)
class Meta:
model = Like
field = ('user', 'post')
def create(self, validated_data):
post = Post(id=validated_data['post'], author=validated_data['user'])
#post=Post.objects.get(pk=validated_data['post'])
post.rating += 1
print(post)
post.save()
return Like.objects.create(**validated_data)
And I get error, when i trying to save Like object TypeError: int() argument must be a string or a number, not 'Post'
Trying to add int(), but it not helps, I think I not correct update Post object
Traceback (most recent call last):
File "/Library/Python/2.7/site-packages/django/core/handlers/base.py", line 149, in get_response
response = self.process_exception_by_middleware(e, request)
File "/Library/Python/2.7/site-packages/django/core/handlers/base.py", line 147, in get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Library/Python/2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
return view_func(*args, **kwargs)
File "/Library/Python/2.7/site-packages/django/views/generic/base.py", line 68, in view
return self.dispatch(request, *args, **kwargs)
File "/Library/Python/2.7/site-packages/rest_framework/views.py", line 466, in dispatch
response = self.handle_exception(exc)
File "/Library/Python/2.7/site-packages/rest_framework/views.py", line 463, in dispatch
response = handler(request, *args, **kwargs)
File "/Library/Python/2.7/site-packages/rest_framework/decorators.py", line 53, in handler
return func(*args, **kwargs)
File "/Users/olegklimakov/Documents/6rp/likes/views.py", line 19, in send_like
serializer.save(user=request.user, isLiked=True)
File "/Library/Python/2.7/site-packages/rest_framework/serializers.py", line 191, in save
self.instance = self.create(validated_data)
File "/Users/olegklimakov/Documents/6rp/likes/serializers.py", line 39, in create
post.save()
File "/Library/Python/2.7/site-packages/django/db/models/base.py", line 700, in save
force_update=force_update, update_fields=update_fields)
File "/Library/Python/2.7/site-packages/django/db/models/base.py", line 728, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/Library/Python/2.7/site-packages/django/db/models/base.py", line 793, in _save_table
forced_update)
File "/Library/Python/2.7/site-packages/django/db/models/base.py", line 823, in _do_update
filtered = base_qs.filter(pk=pk_val)
File "/Library/Python/2.7/site-packages/django/db/models/query.py", line 790, in filter
return self._filter_or_exclude(False, *args, **kwargs)
File "/Library/Python/2.7/site-packages/django/db/models/query.py", line 808, in _filter_or_exclude
clone.query.add_q(Q(*args, **kwargs))
File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py", line 1243, in add_q
clause, _ = self._add_q(q_object, self.used_aliases)
File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py", line 1269, in _add_q
allow_joins=allow_joins, split_subq=split_subq,
File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py", line 1203, in build_filter
condition = self.build_lookup(lookups, col, value)
File "/Library/Python/2.7/site-packages/django/db/models/sql/query.py", line 1099, in build_lookup
return final_lookup(lhs, rhs)
File "/Library/Python/2.7/site-packages/django/db/models/lookups.py", line 19, in __init__
self.rhs = self.get_prep_lookup()
File "/Library/Python/2.7/site-packages/django/db/models/lookups.py", line 57, in get_prep_lookup
return self.lhs.output_field.get_prep_lookup(self.lookup_name, self.rhs)
File "/Library/Python/2.7/site-packages/django/db/models/fields/__init__.py", line 744, in get_prep_lookup
return self.get_prep_value(value)
File "/Library/Python/2.7/site-packages/django/db/models/fields/__init__.py", line 976, in get_prep_value
return int(value)
TypeError: int() argument must be a string or a number, not 'Post'
Post model:
class Post(models.Model):
id = models.AutoField(primary_key=True)
date_create = models.DateField(auto_now_add=True)
date_change = models.DateField(auto_now=True)
title = models.CharField(max_length=250) # Max Length of title = 250
description = models.CharField(max_length=1000) # Max Length = 1000 chars
rating = models.IntegerField(default=1)
author = models.ForeignKey('extuser.ExtUser', blank=True, null=True)
def __unicode__(self):
return u"%s" % self.id

Answer 1

It seems like inside the statement
"Post(id=validated_data['post'], author=validated_data['user'])",
validated_data['post'] gives you a Post object, not a int object,
but the 'id' inside the Post model expect a int object.
That probably is the reason you get the error.

Answer 2

#transactional
def create(self, validated_data):
post = Post(id=validated_data['post'], author=validated_data['user'])
post.rating += 1
post.save()
return super(self, LikeSerializer).create(validated_data)
Its good to let ModelSerializer create do its job, also note you definitely want to use transaction to keep data consistent
Also, code below creates new Post entity:
post = Post(...)
post.save()
You definitely need to get existent Post entity instead
Post.objects.filter(...).first()