使用序列化程序Django（DRF）创建对象

我正在尝试使用序列化程序在视图中创建对象。 但是，我的一个对象有一个恼人的问题：

以下是我创建对象的方式：

editObject=问题\u编辑(
问题，
description='CREATE Question:%s'%Question.text，
编辑器=用户，
注释=问题注释
)
打印（编辑对象）#返回“问题”(编辑对象（无）)
serializer=Question\u editSerializer（editObject）
json=JSONRenderer（）.render（serializer.data）
stream=io.BytesIO（json）
data=JSONParser（）.parse（流）
序列化程序=问题\u编辑序列化程序（数据=数据）
serializer.is\u有效（raise\u exception=True）
serializer.save（）

这是我的

问题\u editSerializer

：

类问题\u editSerializer（serializers.ModelSerializer）：
时间\u自\u编辑=序列化程序。SerializerMethodField（）
类元：
模型=问题\编辑
fields=“\uuuu all\uuuuuu”
def get_time_自编辑以来（自我、对象）：
date\u edit=object.date
time_delta=timesince（日期编辑，时区.now（））
返回时间δ
def创建（自我验证的_数据）：
返回问题\u编辑.objects.create（**已验证的\u数据）

和我的

问题\u编辑

模型：

课堂问题\u编辑（models.Model）：
日期=型号。日期时间字段（自动\u现在\u添加=真）
问题=models.ForeignKey（问题，on_delete=models.CASCADE）
description=models.TextField（最大长度=500）
编辑器=models.ForeignKey(
CustomUser，on_delete=models.SET_NULL，NULL=True）
notes=models.TextField（最大长度=500，空白=True，空=True）

由于在上面的第一段代码中尝试使用序列化程序创建对象，因此出现以下错误：

  File "/foodbook24-api/questions/api/serializers.py", line 44, in get_time_since_edit
    time_delta = timesince(date_edit, timezone.now())
  File "/usr/local/lib/python3.8/site-packages/django/utils/timesince.py", line 49, in timesince
    d = datetime.datetime(d.year, d.month, d.day)

Exception Type: AttributeError at /api/questionnaires/
Exception Value: 'NoneType' object has no attribute 'year'

完全回溯：

Environment:


Request Method: POST
Request URL: http://localhost:8000/api/questionnaires/

Django Version: 3.1.3
Python Version: 3.8.6
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'django.contrib.sites',
 'rest_framework',
 'rest_framework.authtoken',
 'drfpasswordless',
 'allauth',
 'allauth.account',
 'allauth.socialaccount',
 'rest_auth',
 'rest_auth.registration',
 'django_filters',
 'corsheaders',
 'surveys',
 'questionnaire',
 'questions',
 'users',
 'foods',
 'utilities']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'corsheaders.middleware.CorsMiddleware',
 '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/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/base.py", line 179, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 509, in dispatch
    response = self.handle_exception(exc)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 469, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
    raise exc
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/generics.py", line 242, in post
    return self.create(request, *args, **kwargs)
  File "/foodbook24-api/questionnaire/api/views.py", line 184, in create
    return self.elaborateClientPOSTRequest(request)
  File "/foodbook24-api/questionnaire/api/views.py", line 114, in elaborateClientPOSTRequest
    self.create_question_edit_record(questionObject, request)
  File "/foodbook24-api/questionnaire/api/views.py", line 85, in create_question_edit_record
    json = JSONRenderer().render(serializer.data)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 548, in data
    ret = super().data
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 246, in data
    self._data = self.to_representation(self.instance)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 515, in to_representation
    ret[field.field_name] = field.to_representation(attribute)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/fields.py", line 1870, in to_representation
    return method(value)
  File "/foodbook24-api/questions/api/serializers.py", line 44, in get_time_since_edit
    time_delta = timesince(date_edit, timezone.now())
  File "/usr/local/lib/python3.8/site-packages/django/utils/timesince.py", line 49, in timesince
    d = datetime.datetime(d.year, d.month, d.day)

Exception Type: AttributeError at /api/questionnaires/
Exception Value: 'NoneType' object has no attribute 'year'

---

我在这里遗漏了什么？

在下面的代码中，您忘记保存

editObject

：

editObject = Question_edit(
    question=question,
    description='CREATE Question: %s' % question.text,
    editor=user,
    notes=question.notes
)
print(editObject)      # return 'Question_edit object (None)'

serializer = Question_editSerializer(editObject)
json = JSONRenderer().render(serializer.data)
stream = io.BytesIO(json)
data = JSONParser().parse(stream)
serializer = Question_editSerializer(data=data)
serializer.is_valid(raise_exception=True)
serializer.save()

只有当对象保存到数据库时，Django才会计算日期并将其存储在

editObject.date

中。由于没有发生这种情况，只要访问上面的

序列化程序.data

，您的

get\u time\u-Since\u edit（）

方法就会尝试计算

None

和

timezone.now（）

，导致错误

'NoneType'对象没有属性'year'

您可以通过将上述代码更改为以下代码来解决此问题：

editObject = Question_edit(
    question=question,
    description='CREATE Question: %s' % question.text,
    editor=user,
    notes=question.notes
)

editObject.save() # This will populate the `date` attribute with the current date/time

serializer = Question_editSerializer(editObject)
json = JSONRenderer().render(serializer.data)
stream = io.BytesIO(json)
data = JSONParser().parse(stream)
serializer = Question_editSerializer(data=data)
serializer.is_valid(raise_exception=True)
serializer.save()

---

在以下代码中，您忘记保存

editObject

：

editObject = Question_edit(
    question=question,
    description='CREATE Question: %s' % question.text,
    editor=user,
    notes=question.notes
)
print(editObject)      # return 'Question_edit object (None)'

serializer = Question_editSerializer(editObject)
json = JSONRenderer().render(serializer.data)
stream = io.BytesIO(json)
data = JSONParser().parse(stream)
serializer = Question_editSerializer(data=data)
serializer.is_valid(raise_exception=True)
serializer.save()

只有当对象保存到数据库时，Django才会计算日期并将其存储在

editObject.date

中。由于没有发生这种情况，只要访问上面的

序列化程序.data

，您的

get\u time\u-Since\u edit（）

方法就会尝试计算

None

和

timezone.now（）

，导致错误

'NoneType'对象没有属性'year'

您可以通过将上述代码更改为以下代码来解决此问题：

editObject = Question_edit(
    question=question,
    description='CREATE Question: %s' % question.text,
    editor=user,
    notes=question.notes
)

editObject.save() # This will populate the `date` attribute with the current date/time

serializer = Question_editSerializer(editObject)
json = JSONRenderer().render(serializer.data)
stream = io.BytesIO(json)
data = JSONParser().parse(stream)
serializer = Question_editSerializer(data=data)
serializer.is_valid(raise_exception=True)
serializer.save()