mongodb GridFS django FileFiled 默认 widget 只有一个文件上传框显示不了字段内容，重写widget

首先，定位到：FileFiled 默认 widget 源码：mongoadmin包options.py中，如下：

 # Defaults for formfield_overrides. ModelAdmin subclasses can change this
 # by adding to ModelAdmin.formfield_overrides.
 FORMFIELD_FOR_DBFIELD_DEFAULTS = {
     DateTimeField: {
         'form_class': forms.SplitDateTimeField,
         'widget'    : widgets.AdminSplitDateTime
         },
     URLField     : {'widget': widgets.AdminURLFieldWidget},
     IntField     : {'widget': widgets.AdminIntegerFieldWidget},
     ImageField   : {'widget': widgets.AdminFileWidget},
     FileField    : {'widget': widgets.AdminFileWidget},
     }

 _fieldgenerator = load_field_generator()()

源码摘取

然后，根据注释部分：

# Defaults for formfield_overrides. ModelAdmin subclasses can change this
# by adding to ModelAdmin.formfield_overrides.

重写widget如下：

 from django.contrib.admin.widgets import AdminFileWidget
 class FileWidget(AdminFileWidget):
     """
     A FileField Widget that shows its current value if it has one.
     """

     def __init__(self, attrs={}):
         super(FileWidget, self).__init__(attrs)

     def render(self, name, value, attrs=None):
         output = []
         output.append(super(FileWidget, self).render(name, value, attrs))
         output.append('<p class="help"><textarea name="%s" id="id_%s" rows="10" cols="40" class="vLargeTextField"> %s </textarea></p>' % (name, name, value.read()))
         return mark_safe(u''.join(output))

MyFileWidget

引入widget如下：

 from mongoengine import Document
 class AbstractDocument(Document):

     ModelAdmin.formfield_overrides = {
         FileField: {'widget': FileWidget},
     }

     meta = {
         'abstract': True,
     }

MyDocument