问题

我有 2 个模型、线索和注释。我希望潜在客户能够拥有 1 个或多个注释。我使用了通用外键，因为我想为 future 做计划，并且可以分配一个注释来说明一个人或一个 session 。

按照 django rest framework 和 Rest Framework Generic Relations 的说明，我正在尝试从另一个序列化程序导入一个序列化程序，以使反向关系成为可能。

错误

我无法在两个文件中导入序列化器(从另一个调用一个序列化器)，因为我得到:

File "/Users/james/Documents/UtilityCRM-Server/crm/leads/urls.py", line 2, in <module>
    from leads import views
  File "/Users/james/Documents/UtilityCRM-Server/crm/leads/views.py", line 11, in <module>
    from leads.serializers import LeadSerializer
  File "/Users/james/Documents/UtilityCRM-Server/crm/leads/serializers.py", line 4, in <module>
    from notes.serializers import NoteSerializer
  File "/Users/james/Documents/UtilityCRM-Server/crm/notes/serializers.py", line 6, in <module>
    from leads.serializers import LeadSerializer
ImportError: cannot import name LeadSerializer

这很奇怪，因为如果我打开 django shell 并运行以下命令，它可以让我将它们全部导入:

from leads.serializers import LeadSerializer
from notes.serializers import NotesSerializer
from callbacks.serializers import CallbackSerializer

如有任何帮助，我们将不胜感激!

代码

这是我的设置文件的已安装应用部分:

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    # 3rd Party Apps
    'rest_framework',
    'generic_relations',
    # My Apps
    'leads.apps.LeadsConfig',
    'callbacks.apps.CallbacksConfig',
    'notes.apps.NotesConfig',
]

notes/models.py

from __future__ import unicode_literals

from django.db import models
from django.utils import timezone
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType

class Note(models.Model):
    author = models.ForeignKey('auth.User')
    title = models.CharField(max_length=100)
    text = models.TextField()
    created_date = models.DateTimeField(default=timezone.now)

    # Relations
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    note_object = GenericForeignKey('content_type', 'object_id')

    def __str__(self):
        return self.title

leads/models.py

from __future__ import unicode_literals

from django.db import models
from django.contrib.contenttypes.fields import GenericRelation
from django.utils import timezone

from notes.models import Note
from callbacks.models import Callback

GAS = 'G'
ELECTRICITY = 'E'
LEAD_TYPE_CHOICES = (
    (GAS, 'Gas'),
    (ELECTRICITY, 'Electricity'),
)

# Create your models here.
class Lead(models.Model):

    author = models.ForeignKey('auth.User')
    type = models.CharField(
        max_length=1,
        choices=LEAD_TYPE_CHOICES,
        default=GAS,
    )
    business_registration_number = models.IntegerField(max_length=20)
    business_name = models.CharField(max_length=50)
    mpan = models.IntegerField(max_length=21)
    supplier = models.CharField(max_length=45)
    contract_length = models.IntegerField(max_length=2)
    contract_start_date = models.DateField()
    contract_end_date = models.DateField()
    address_line_1 = models.CharField(max_length=45)
    address_line_2 = models.CharField(max_length=45)
    address_line_3 = models.CharField(max_length=45)
    address_city = models.CharField(max_length=45)
    address_county = models.CharField(max_length=45)
    address_postcode = models.CharField(max_length=10)
    contact_title = models.CharField(max_length=45)
    contact_first_name = models.CharField(max_length=45)
    contact_middle_name = models.CharField(max_length=45)
    contact_last_name = models.CharField(max_length=45)
    contact_telephone = models.IntegerField(max_length=11)
    contact_email = models.EmailField(max_length=60)
    created_date = models.DateTimeField(default=timezone.now)

    # Relations
    assigned_to = models.ForeignKey('auth.User', related_name='+')
    #from_batch = models.ForeignKey('data_batch.DataBatch', related_name='+')
    #callbacks = GenericRelation(Callback)
    notes = GenericRelation(Note)

    class Meta:
        ordering = ('contract_end_date', 'business_name',)

    def __str__(self):
        return self.business_name

我有 2 个序列化程序:

leads/serializers.py

from rest_framework import serializers
from leads.models import Lead, LEAD_TYPE_CHOICES

from notes.serializers import NoteSerializer

class LeadSerializer(serializers.ModelSerializer):
    notes = NoteSerializer(many=True, read_only=True)

    class Meta:
        model = Lead
        fields = (
            'id',
            'business_name',
            'business_registration_number',
            'supplier',
            'contract_length',
            'contract_start_date',
            'notes'
            )

notes/serializers.py

from generic_relations.relations import GenericRelatedField
from rest_framework import serializers
from notes.models import Note

from leads.models import Lead
from leads.serializers import LeadSerializer

from callbacks.models import Callback
from callbacks.serializers import CallbackSerializer


class NoteSerializer(serializers.ModelSerializer):
    """
    A `Note` serializer with a `GenericRelatedField` mapping all possible
    models to their respective serializers.
    """
    note_object = GenericRelatedField({
        Lead: LeadSerializer(),
        Callback: CallbackSerializer()
    })

    class Meta:
        model = Note
        fields = (
            'id',
            'author',
            'title',
            'text',
            'created_date',
            'note_object',
            )

最佳答案

正如我之前在评论中提到的，我相信这是由于 Python 中的循环(循环)导入造成的。 当您在模型中声明相关字段并且某些模型尚未实例化时，尤其会发生这种情况。

在这种情况下，当您执行程序时，它会尝试导入 LeadSerializer，这需要导入 NoteSerializer，即需要导入 LeadSerializer，这需要导入 NoteSerializer...看看这是怎么回事？

你的堆栈轨迹说明了一切:

from leads.serializers import LeadSerializer

from notes.serializers import NoteSerializer

from leads.serializers import LeadSerializer

正在生成ImportError:无法导入名称 LeadSerializer

我为解决此问题所做的工作是在单个文件中声明所有序列化程序。因此，您有两个选择:

1. 将 LeadSerializer 移动到 notes/serializers.py
2. 将 NoteSerializer 移动到 leads/serializers.py

这不是解决这个问题的最优雅的方法，但它已经达到了目的。

下面的部分没有提供关于如何解决这个问题的进一步解释，而是对这个问题的观察。

也许 Django 和 DRF 将来可以提供避免这种情况的方法，例如将序列化程序声明为

note_object = GenericRelatedField({
    Lead: 'leads.serializers'.LeadSerializer,
    Callback: CallbackSerializer()
})

或

notes = 'notes.serializers'.NoteSerializer(many=True, read_only=True)

关于python - 无法从 django rest-framework 中的其他序列化程序导入序列化程序？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42046550/