无法使用类型值设置 MODEL_NAME SpatialProxy (POLYGON)：<class 'django.contrib.gis.geos.polygon.Polygon'>答案

【问题标题】：Cannot set MODEL_NAME SpatialProxy (POLYGON) with value of type: <class 'django.contrib.gis.geos.polygon.Polygon'>无法使用类型值设置 MODEL_NAME SpatialProxy (POLYGON)：<class 'django.contrib.gis.geos.polygon.Polygon'>
【发布时间】：2019-04-01 09:15:10
【问题描述】：

当我尝试对我的一个模型的 url 进行 API 调用时，我面临以下问题：

Cannot set Allotment SpatialProxy (POLYGON) with value of type: <class 'django.contrib.gis.geos.polygon.Polygon'>

我在 PGadmin 中检查模型的定义和数据类型。

完整日志

Traceback:

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/core/handlers/exception.py" in inner
  35.             response = get_response(request)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/core/handlers/base.py" in _get_response
  128.                 response = self.process_exception_by_middleware(e, request)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/core/handlers/base.py" in _get_response
  126.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/views/decorators/csrf.py" in wrapped_view
  54.         return view_func(*args, **kwargs)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/rest_framework/viewsets.py" in view
  103.             return self.dispatch(request, *args, **kwargs)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/rest_framework/views.py" in dispatch
  483.             response = self.handle_exception(exc)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/rest_framework/views.py" in handle_exception
  443.             self.raise_uncaught_exception(exc)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/rest_framework/views.py" in dispatch
  480.             response = handler(request, *args, **kwargs)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/rest_framework/mixins.py" in list
  42.         page = self.paginate_queryset(queryset)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/rest_framework/generics.py" in paginate_queryset
  173.         return self.paginator.paginate_queryset(queryset, self.request, view=self)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/rest_framework/pagination.py" in paginate_queryset
  337.         return list(queryset[self.offset:self.offset + self.limit])

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/db/models/query.py" in __iter__
  272.         self._fetch_all()

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/db/models/query.py" in _fetch_all
  1179.             self._result_cache = list(self._iterable_class(self))

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/db/models/query.py" in __iter__
  63.             obj = model_cls.from_db(db, init_list, row[model_fields_start:model_fields_end])

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/db/models/base.py" in from_db
  507.         new = cls(*values)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/db/models/base.py" in __init__
  424.                 _setattr(self, field.attname, val)

File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/contrib/gis/db/models/proxy.py" in __set__
  75.                 instance.__class__.__name__, gtype, type(value)))

Exception Type: TypeError at /api/cutarea-allotment/
Exception Value: Cannot set Allotment SpatialProxy (POLYGON) with value of type: <class 'django.contrib.gis.geos.polygon.Polygon'>

这是模型的定义：

from renter.models import *
from classification_list.models import*
from django.contrib.gis.db import models
from django.contrib.gis.geos import Polygon
...

class All(models.Model): 
    geom = models.PolygonField(geography=True, null=True, blank=True, verbose_name='geom')
    num_kvr = models.ForeignKey(QartalKeys, models.DO_NOTHING, blank=True, null=True)
    allot_num = models.SmallIntegerField(blank=True, null=True)

怎么了？对于这个问题，我没有找到相关的问题或有用的建议。谢谢。

【问题讨论】：

不是这个特定问题的答案，但可能对其他人有帮助：当我尝试添加一个 gdal 多边形时，我遇到了一个非常相似的错误geos 多边形 - 它们在堆栈跟踪中看起来非常相似！

标签： django postgis geodjango

【解决方案1】：

问题一定与PolygonField的geography=True参数有关。
阅读documentation about geography enabled fields，我们看到以下内容：

geography 类型为使用地理坐标（例如 WGS84 经度/纬度）表示的空间特征提供本机支持。 与几何类型使用的平面不同，geography 类型使用其球面表示数据。在地理列上执行的距离和测量操作会自动采用大圆弧计算并返回线性单位。换句话说，当在两个地理上调用 ST_Distance 时，会返回一个以米为单位的值（与在 WGS84 中的几何列上调用度数相反）。

由于您将字段设置为期望 geography 类型的对象，然后您尝试传递多边形的非地理表示，因此您会收到错误。

【讨论】：