标签: generic-foreign-key

我需要在应用程序问题中执行模型答案的数据迁移.在该脚本中存在依赖性,因此我需要创建应用程序日记中的模型章的实例.所以,我把它编码如下:

def forwards(self, orm):
    for answer_object in orm.Answer.objects.all():

        #This Works.
        blog, is_created = orm['blog.Post'].objects.get_or_create(title=answer_object.answer[:100])
        blog.save()

        #This DOES NOT work
        chapter, is_created = orm['journal.Chapter'].objects.get_or_create(content_object=blog)
        chapter.save()
        #cleanup task, not relevant to this question below
        answer_object.chapter_ptr = chapter
        answer_object.save()

但正如预期的那样,这会在"orm ['journal.Chapter']上引发错误.objects.get_or_create(content_object = blog)"

django.core.exceptions.FieldError: Cannot resolve keyword 'content_object' into field.

这可能是由于content_object是GenericForeignKey,因此不允许进行某些操作.但我也尝试了其他替代方法来创建"章节"对象,比如

chapter = orm['journal.Chapter'](content_object=blog)
ERROR > TypeError: 'content_object' is an invalid keyword argument for this function

和

chapter = orm.journal.Chapter(content_object=blog)
 ERROR > AttributeError: The model …

我有以下概念模型:

class GenericAbstractBase(models.Model):
    name = models.CharField(max_length=255)
    staff = generic.GenericRelation(
        "Staff",
        content_type_field="content_type",
        object_id_field="object_id",
    )

    class Meta:
        abstract = True


class GenericModelA(GenericAbstractBase):
    extra_a = models.CharField(max_length=255)


class GenericModelB(GenericAbstractBase):
    extra_b = models.CharField(max_lenth=10)


class Staff(models.Model):

    first_name = models.CharField(max_length=255)
    last_name = models.CharField(max_length=255)
    active = models.CharField(max_length=10, choices = ACTIVE_CHOICES)

    limit = models.Q(app_label='staff', model='genericmodela') | models.Q(app_label='staff', model='genericmodelb')
    content_type = models.ForeignKey(ContentType, limit_choices_to=limit)
    object_id = models.PositiveIntegerField()
    generic_object = generic.GenericForeignKey("content_type", "object_id")

在Django v1.4和Django v1.5中,以下查询工作正常:

>>> ctype = ContentType.objects.get_for_model(GenericModelA)
>>> Staff.objects.filter(
        content_type=ctype,
        genericmodela__name__icontains="a"
    )
>>> [<Staff: Abbott, Kaylee>, <Staff: Adams, Kay>, ... …

我正在研究Django的讨论应用程序,它有线程,帖子,回复和投票.投票使用通用外键和内容类型来确保用户只能在特定的线程/帖子/回复上投票一次.

投票模型如下所示:

VOTE_TYPE = (
    (-1, 'DISLIKE'),
    (1, 'LIKE'),
)

class Vote(models.Model):
    user = models.ForeignKey(User)
    content_type = models.ForeignKey(ContentType,
        limit_choices_to={"model__in": ("Thread", "Reply", "Post")}, 
        related_name="votes")
    object_id = models.PositiveIntegerField()
    content_object = generic.GenericForeignKey('content_type', 'object_id')
    vote = models.IntegerField(choices=VOTE_TYPE)

    objects = GetOrNoneManager()

    class Meta():
        unique_together = [('object_id', 'content_type', 'user')]

投票序列化器:

class VoteSerializer(serializers.ModelSerializer):
    class Meta:
        model = Vote

处理投票的观点:

@api_view(['POST'])
def discussions_vote(request):

if not request.user.is_authenticated():
    return Response(status=status.HTTP_404_NOT_FOUND)

data = request.DATA

if data['obj_type'] == 'thread':
    content_type = ContentType.objects.get_for_model(Thread)

    print content_type.id

    info = {
        'content_type': content_type.id,
        'user': …

我在模型上使用Generic Relation并尝试使用Django Rest Framework对其进行序列化.但是,执行以下操作会给我一个属性错误:

'GenericForeignKey' object has no attribute 'field'

models.py

class AdditionalInfo():

    #other fields

    seal_type = models.ForeignKey(ContentType,
        related_name='seal'
    )
    seal_id = models.PositiveIntegerField(null=True)
    seal = generic.GenericForeignKey(
                                'seal_type',
                                'seal_id')

serializers.py

class AdditionalInfoSerializer():
    seal = serializers.Field(source='seal')

我究竟做错了什么？我在django rest框架文档中找不到相关内容.

我想为Comment具有GenericForeignKey关系的model()创建数据迁移.我的模型是根据django文档为contenttypes制作的.

楷模:

...
class NiceMeme(models.Model):
    """
        Example model.
    """

    name = models.CharField(max_length=140)
    image = models.ImageField(upload_to=get_path_to_store_nice_meme_images)


class Comment(models.Model):
    """
        Model to add comments to any other (non abstract) model.
    """
    ...
    user = models.ForeignKey(ExtendedUser)
    content = models.CharField(max_length=140)
    content_type = models.ForeignKey(ContentType)
    object_pk = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_pk')

数据迁移:

...
def create_comment(apps, schema_editor):
    ...
    nice_meme = NiceMeme.objects.create(name='Nice nice meme')
    Comment.objects.create(
        user=user,
        content='Gott ist tot',
        poster_username='Friedrich',
        content_object=nice_meme
    )

...
operations = [
    migrations.RunPython(create_comment)
] …

符号.py

class Symbol(BaseModel):
    name = models.CharField(max_length=30,)

    class Meta:
        abstract = True

class StockSymbol(Symbol):
    market = models.CharField(max_length=10,)
    my_daily_price = GenericRelation(MyDailyPrice)

每日价格.py

class DailyPrice(BaseModel):
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')

    class Meta:
        abstract = True

class MyDailyPrice(DailyPrice):
    open = models.DecimalField(
        max_digits=15,
        decimal_places=2,
    )

我想做的是，

symbol = StockSymbol.objects.first()
MyDailyPrice.objects.filter(content_object=symbol)

但它发生了错误：

FieldError: Field 'content_object' does not generate an automatic reverse relation and therefore cannot be used for reverse querying. If it is a GenericForeignKey, consider adding a GenericRelation.

StockSymbol已经有了 …

Django 的示例代码位于https://docs.djangoproject.com/es/1.9/ref/contrib/contenttypes/

content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
object_id = models.PositiveIntegerField()
content_object = GenericForeignKey('content_type', 'object_id')

显示 object_id 不带db_index=True

虽然object_id可能会用于连接操作。

是db_index=True因为一些关于 GFK 的隐藏代码而被假设吗？或者我应该在需要时包含它？

我正在尝试在 django 中将外键转换为 GenericForeignKey。我计划在三个迁移中执行此操作：mig1、mig2、mig3。

迁移1（mig1）有以下代码

class Migration(migrations.Migration):

    dependencies = [
        ('contenttypes', '0002_remove_content_type_name'),
        ('post_service', '0008_auto_20180802_1112'),
    ]

    operations = [
        migrations.AddField(
            model_name='comment',
            name='content_type',
            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='contenttypes.ContentType'),
        ),
        migrations.AddField(
            model_name='comment',
            name='object_id',
            field=models.PositiveIntegerField(null=True),
        ),
    ]

迁移2（mig2）有以下代码

def change_posts_to_generic_key_comment(apps, schema_editor):
    Comment  = apps.get_model('post_service', 'Comment')
    db_alias = schema_editor.connection.alias
    comments = Comment.objects.using(db_alias).all()
    for comment in comments:
        Comment.objects.filter(id=comment.id).update(content_object=comment.post)

def reverse_change_posts_to_generic_key_comment(apps, schema_editor):
    Comment  = apps.get_model('post_service', 'Comment')
    db_alias = schema_editor.connection.alias
    comments = Comment.objects.using(db_alias).all()
    for comment in comments:
        Comment.objects.filter(id=comment.id).update(content_object=)

class Migration(migrations.Migration):

    dependencies = [
        ('post_service', '0009_auto_20180802_1623'),
    ]

    operations = [
        migrations.RunPython(change_posts_to_generic_key_comment, …

我正在用头撞墙试图设置通用外键。我将发布尽可能多的代码，我将在一小时内重试。

我已经阅读了该文档一百万次，但它似乎没有帮助。

我认为这就是我正在做的事情。

def create_stream(request):
    stream_form = StreamForm()
    comment_form = CommentDataForm()

    if request.POST:    
        stream_form = StreamForm(request.POST)
        comment_form = CommentDataForm(request.POST)    
        if stream_form.is_valid() and comment_form.is_valid():

            attempt = comment_form.save()

            stream_form.save(commit=False)
            stream_form.content_object = attempt
            stream_form.save()

            return HttpResponseRedirect('/main/')
        else:
            HttpResponse('Nope')

    context = {'form1':stream_form, 'form2':comment_form}
    template = 'nregistration.html'
    return render(request, template, context)

这些表单都是 ModelForm（为了便于使用，所以我可以使用保存功能）。他们看起来像这样

class StreamForm(forms.ModelForm):
    class Meta:
        model = Stream
        exclude = ['object_id', 'content_object']

class CommentDataForm(forms.ModelForm):
    class Meta:
        model = CommentData

我的相关课程看起来像这样

class Stream(models.Model):
    uid = models.CharField(max_length=20, null=True, blank=True)
    str_type = models.CharField(max_length=120, default='ABC')
    creator = …

我在我的模型中定义了以下内容：

class TaskLink(models.Model):
    task = model.ForeignKey(Task)
    link_choices = (
        models.Q(app_label="accounts", model="location"),
        # Other models are also linked to here.
    )
    linked_content_type = \
        models.ForeignKey(
            ContentType,
            limit_choices_to=link_choices
        )
    linked_object_id = models.PositiveIntegerField()
    linked_object = \
        generic.GenericForeignKey(
            'linked_object_content_type',
            'linked_object_id'
        )

该模型将Task对象与元组中的任何模型链接起来link_choices。在本例中，该accounts.Location模型在此列表中。

当删除一个Location对象导致相关对象的级联删除时，我的问题就出现了TaskLink。删除失败并出现以下错误消息：

django.core.exceptions.FieldError: Cannot resolve keyword 'object_id' into field. Choices are: id, linked_object, linked_object_content_type, linked_object_content_type_id, linked_object_id, task, task_id

视图是django.views.generic.DeleteView仅包含pk_url_kwarg参数和模型集的实例（以及添加到调度方法中的权限装饰器）；TaskLink在我将模型添加到混合中之前，它可以正常工作 linked_object_fine 。

我缺少什么？

编辑：这似乎可能是 Django 中的一个错误；当通过通用外键级联删除对象时，Django 会忽略传递给字段构造函数的字段名称字符串GenericForeignKey …