在多个应用中使用流场：迁移错误

Question

我的鹡鸰网站项目是在不同的应用程序拆分，像core，event，publications等等，我建立了我的streamfield中core.models。

现在我想不仅core.models在event.models.

但是，只定义StreamBlock一次流场（子类化）并在所有应用程序中重用它的最优雅（干）方式是什么？

我StreamBlock的灵感来自wagtaildemo项目：

# core/models.py
class StoryBlock(StreamBlock):
    h2 = CharBlock(icon="title", classname="title")
    h3 = CharBlock(icon="title", classname="title")
    h4 = CharBlock(icon="title", classname="title")
    intro = RichTextBlock(icon="pilcrow")
    paragraph = RichTextBlock(icon="pilcrow")
    aligned_image = ImageBlock(label="Aligned image")
    pullquote = PullQuoteBlock()
    read_on = ReadOnBlock()

——

# event/models.py
from wagtail.wagtailcore.fields import StreamField
from wagtail.wagtailadmin.edit_handlers import FieldPanel, StreamFieldPanel
from core.models import StoryBlock

class EventIndexPage(Page):
    body = StreamField(StoryBlock())

    content_panels = Page.content_panels + [
        StreamFieldPanel('body'),
    ]

但是尝试makemigrations更新的EventIndexPage页面模型会产生一个警告，我是trying to add a non-nullable field 'body' to eventindexpage without a default- 但这只会发生在非core模型上的（流）字段上。

传递请求的默认值 - 无论是它"asdf"还是"[]"- 来makemigrations构建迁移文件，但以下migrate失败：

$ python manage.py migrate
...
  File "/myproject/venv/lib/python3.5/site-packages/wagtail/wagtailcore/fields.py", line 90, in get_prep_value
    return json.dumps(self.stream_block.get_prep_value(value), cls=DjangoJSONEncoder)
  File "/myproject/venv/lib/python3.5/site-packages/wagtail/wagtailcore/blocks/stream_block.py", line 205, in get_prep_value
    for child in value  # child is a BoundBlock instance
  File "/myproject/venv/lib/python3.5/site-packages/wagtail/wagtailcore/blocks/stream_block.py", line 205, in <listcomp>
    for child in value  # child is a BoundBlock instance
AttributeError: 'str' object has no attribute 'block'

完整追溯

如果这与我的问题有关：这个项目将部署到 openshift，所以我在使用 Python 3 时仅限于 Django 1.8。很高兴使用 wagtail 1.5。

Answer 1

正如gasman在他的评论中指出的那样，使用""作为迁移的默认值可以解决问题。