如何在Django管理后台显示ManyToMany关系的raw_id值？

Question

我有一个应用程序，里面用到了原始ID（raw_id）来处理外键（ForeignKeyField）和多对多关系（ManyToManyField）。在管理界面中，外键的值会显示在编辑框的右侧。

可惜的是，这个功能在多对多关系中并不好用。我检查过代码，觉得这应该是正常的表现。不过，我想知道有没有简单的方法可以改变这种情况？

提前谢谢大家！

更新：我尝试去扩展（subclass）ManyToManyRawIdWidget，但我不知道怎么让原始ID字段使用我自定义的控件。formfield_overrides好像对原始ID字段不起作用。

Answer 1

这个方法适用于Django 1.11及更高版本。

from django.contrib.admin.sites import site
from django.contrib.admin.widgets import ManyToManyRawIdWidget
from django.core.urlresolvers import reverse, NoReverseMatch
from django.utils.safestring import mark_safe


class VerboseManyToManyRawIdWidget(ManyToManyRawIdWidget):

    def label_and_url_for_value(self, value):
        result = []
        for v in value:
            key = self.rel.get_related_field().name
            try:
                obj = self.rel.model._default_manager.using(self.db).get(**{key: v})
            except (ValueError, self.rel.model.DoesNotExist):
                return '', ''

            try:
                url = reverse(
                    '{}:{}_{}_change'.format(self.admin_site.name, obj._meta.app_label,
                                             obj._meta.object_name.lower()),
                    args=(obj.pk,))
            except NoReverseMatch:
                url = ''  # Admin not registered for target model.

            result.append('<strong><a href="{}">{}</a></strong>'.format(url,  str(obj)))

        return mark_safe('; '.join(result)), ''


class VerboseRawIdManyToManyAdminMixin:
    def formfield_for_dbfield(self, db_field, **kwargs):
        if db_field.name in self.raw_id_fields:
            kwargs.pop('request', None)
            if db_field.rel.__class__.__name__ == 'ManyToManyRel':
                kwargs['widget'] = VerboseManyToManyRawIdWidget(db_field.rel, site)
            return db_field.formfield(**kwargs)
        return super().formfield_for_dbfield(db_field, **kwargs)

另外，还有一个Django应用可以实现这个功能 django-salmonella

Answer 2

最后我终于让它工作了。这里是更新后的Django 2.0版本

from django.contrib.admin.widgets import ManyToManyRawIdWidget
from django.utils.encoding import smart_str
from django.urls import reverse
from django.utils.html import escape, mark_safe


class VerboseManyToManyRawIdWidget(ManyToManyRawIdWidget):
    """
    A Widget for displaying ManyToMany ids in the "raw_id" interface rather 
    than in a <select multiple> box. Display user-friendly value like the ForeignKeyRawId widget
    """

    def __init__(self, remote_field, attrs=None, *args, **kwargs):
        super().__init__(remote_field, attrs, *args, **kwargs)

    def label_and_url_for_value(self, value):
        values = value
        str_values = []
        field = self.rel.get_related_field()
        key = field.name
        fk_model = self.rel.model
        app_label = fk_model._meta.app_label
        class_name = fk_model._meta.object_name.lower()
        for the_value in values:
            try:
                obj = fk_model._default_manager.using(self.db).get(**{key: the_value})
                url = reverse('admin:{0}_{1}_change'.format(app_label, class_name), args=[obj.id])
                label = escape(smart_str(obj))
                elt = '<a href="{0}" {1}>{2}</a>'.format(
                    url,
                    'onclick="return showAddAnotherPopup(this);" target="_blank"',
                    label
                )
                str_values += [elt]
            except fk_model.DoesNotExist:
                str_values += [u'???']
        return mark_safe(', '.join(str_values)), ''


class MyAdmin(admin.ModelAdmin):
     ...
     def formfield_for_dbfield(self, db_field, **kwargs):
         if db_field.name in ('groups', ):
             kwargs['widget'] = VerboseManyToManyRawIdWidget(db_field.remote_field, self.admin_site)
         else:
             return super().formfield_for_dbfield(db_field, **kwargs)
         kwargs.pop('request')
         return db_field.formfield(**kwargs)

可惜，我花了钱却没得到什么好处 ;-)

更新：这个代码片段现在可以和Django 2.0兼容了。你也可以看看 http://djangosnippets.org/snippets/2108/