'tuple'对象在实现序列化程序时没有属性'_meta'

Question

我正在为我的模型实现序列化程序。但我在访问api端点时遇到了这个错误，它说"元组对象没有属性"_meta"；。这是我的模型和序列化程序

型号

class WorkflowStep(models.Model):
name = models.CharField(max_length=200)
workflow = models.ForeignKey('WorkflowType', null=True, blank=True, related_name='workflow', on_delete=models.SET_NULL)
allowed_statuses = models.ManyToManyField("WorkflowStepStatus", null=True, blank=True, related_name='status')
active_status = models.ForeignKey('WorkflowStepStatus', null=True, blank=True,
related_name='active_status', on_delete=models.SET_NULL)
default_status = models.ForeignKey('WorkflowStepStatus', null=True, blank=True,
related_name='default_status', on_delete=models.SET_NULL)
should_recheck = models.BooleanField(null=True, blank=True)
step_type = models.ForeignKey("WorkflowStepType", on_delete=models.SET_NULL, null=True,
blank=True, related_name='step_type')
trigger_on_new_version = models.BooleanField(null=True, blank=True)
id = models.UUIDField(default=uuid.uuid4, editable=False, unique=True, primary_key=True)
def __str__(self):
return self.name + "_" + self.workflow.name

class Prerequisite(models.Model):
workflow_step = models.ForeignKey("WorkflowStep", null=True, blank=True, on_delete=models.CASCADE,
related_name='workflow_step')
pre_requisite_step = models.ForeignKey('WorkflowStep', null=True, blank=True,
on_delete=models.SET_NULL, related_name='pre_requisite_step')
pre_requisite_step_status = models.ManyToManyField("WorkflowStepStatus",
null=True,
blank=True,
related_name='pre_requisite_step_status')
id = models.UUIDField(default=uuid.uuid4, editable=False, unique=True, primary_key=True)
def __str__(self):
return self.workflow_step.name + "_pre_req_" + self.workflow_step.workflow.name

序列化程序

class WorkflowStepSerializer(serializers.ModelSerializer):
workflow = WorkflowTypeSerializer(many=False)
allowed_statuses = WorkflowStepStatusSerializer(many=True)
active_status = WorkflowStepStatusSerializer(many=False)
step_type = WorkflowStepTypeSerializer(many=False)
prerequisite = serializers.SerializerMethodField()
class Meta:
model = WorkflowStep
fields = '__all__'
def get_prerequisite(self, obj):
pre_requisites = obj.workflow_step.all()
serializer = PrerequisiteSerializer(pre_requisites, many=True)
return serializer.data
class PrerequisiteSerializer(serializers.ModelSerializer):
workflow_step = WorkflowStepSerializer(many=True)
pre_requisite_step = WorkflowStepSerializer(many=True)
pre_requisite_step_status = WorkflowStepStatusSerializer(many=True)
class Meta:
model = Prerequisite,
fields = "__all__"

错误

AttributeError at /api/workflowsteps/
'tuple' object has no attribute '_meta'
Request Method: GET
Request URL:    http://127.0.0.1:8000/api/workflowsteps/
Django Version: 3.2.9
Exception Type: AttributeError
Exception Value:    
'tuple' object has no attribute '_meta'
Exception Location: /Users/a/PycharmProjects/freshDjangoProject/venv/lib/python3.9/site-packages/rest_framework/utils/model_meta.py, line 35, in get_field_info
Python Executable:  /Users/a/PycharmProjects/freshDjangoProject/venv/bin/python
Python Version: 3.9.6
Python Path:    
['/Users/a/PycharmProjects/freshDjangoProject',
'/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python39.zip',
'/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9',
'/usr/local/Cellar/python@3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib-dynload',
'/Users/a/PycharmProjects/freshDjangoProject/venv/lib/python3.9/site-packages']
Server time:    Fri, 18 Feb 2022 13:11:19 +0000

Answer 1

class PrerequisiteSerializer(serializers.ModelSerializer):
workflow_step = WorkflowStepSerializer(many=True)
pre_requisite_step = WorkflowStepSerializer(many=True)
pre_requisite_step_status = WorkflowStepStatusSerializer(many=True)
class Meta:
model = Prerequisite, <---- remove comma right there
fields = "__all__"