postgresql 值错误：无法添加 *：实例在数据库“默认”上，值在数据库“无”上
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ValueError: Cannot add *: instance is on database "default", value is on database "None"
提问by super9
In [1]: from editor.models import *
In [4]: from subscriptions.models import *
In [5]: template = StockTemplate.objects.create(name='Template 1')
In [6]: template
Out[6]: <StockTemplate: Template 1>
In [7]: plan = SubscriptionPlan.objects.create(name='Bronze')
In [8]: plan
Out[8]: <SubscriptionPlan: Bronze>
In [12]: plan.templates.add(template)
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/home/me/GitProjects/test_git/proj/<ipython console> in <module>()
/home/me/GitProjects/test_git/django-trunk/django/db/models/fields/related.pyc in add(self, *objs)
498 if rel.through._meta.auto_created:
499 def add(self, *objs):
--> 500 self._add_items(self.source_field_name, self.target_field_name, *objs)
501
502 # If this is a symmetrical m2m relation to self, add the mirror entry in the m2m table
/home/me/GitProjects/test_git/django-trunk/django/db/models/fields/related.pyc in _add_items(self, source_field_name, target_field_name, *objs)
558 if not router.allow_relation(obj, self.instance):
559 raise ValueError('Cannot add "%r": instance is on database "%s", value is on database "%s"' %
--> 560 (obj, self.instance._state.db, obj._state.db))
561 new_ids.add(obj.pk)
562 elif isinstance(obj, Model):
ValueError: Cannot add "<StockTemplate: Template 1>": instance is on database "default", value is on database "None"
Models
楷模
6 class SubscriptionPlan(models.Model):
7 name = models.CharField(max_length=255)
8 templates = models.ManyToManyField(StockTemplate)
9 monthly_fee = models.IntegerField("Monthly Fee", max_length=16, default="0")
10 modified = models.DateTimeField(auto_now=True, editable=False)
11 created = models.DateTimeField(auto_now_add=True, editable=False)
12
13 def __unicode__(self):
14 return "%s" % self.name
18 class StockTemplate(IKImage):
19 name = models.TextField()
20 description = models.TextField(blank=True)
21
22 is_public = models.BooleanField(default=True)
23
24 html = models.FileField(upload_to='stock_templates/html/', \
25 help_text='The file that will be used to render.')
26 #css = models.FileField(upload_to='stock_templates/css/', blank=True)
27
28 img = models.ImageField(upload_to='stock_templates/img/')
29
30 modified = models.DateTimeField(auto_now=True)
31 created = models.DateTimeField(auto_now_add=True)
32
33 objects = StockTemplateManager()
34
35 class IKOptions:
36 spec_module = 'editor.specs'
37 cache_dir = 'stock_templates/img/specs/'
38 image_field = 'img'
39
40 def __unicode__(self):
41 return u"%s" % self.name
42
43 def get_absolute_url(self):
44 return reverse('preview_stock', args=[self.id])
Is it something to do with the fact that StockTemplate is an IKImage object?
这与 StockTemplate 是 IKImage 对象这一事实有关吗？
回答by diegueus9
The problem here is you need call the method save for both objects before add:
这里的问题是您需要在添加之前为两个对象调用 save 方法：
template.save()
plan.save()
plan.templates.add(template)
Django can not add a template of a plan if none of that objects don't have an id
如果没有一个对象没有 id，Django 无法添加计划模板
