如何从Django的内联管理中获取当前模型实例

Question

我正在使用 formfield_for_manytomany 这个功能，它在 Django 的文档 中有介绍。不过在这个函数里，我需要获取当前正在编辑的父对象。

def formfield_for_manytomany(self, db_field, request, **kwargs):
    if db_field.name == "car":
        kwargs["queryset"] = Cars.objects.filter(owner=person)
    return super(myModel, self).formfield_for_manytomany(db_field, request, **kwargs)

我该如何获取正在编辑的这个人呢？

Answer 1

为了访问InlineModelAdmin的父类ModelAdmin的模型实例，我以前用过这个小技巧：

class PersonAdmin(ModelAdmin):
    def get_formsets(self, request, obj=None, *args, **kwargs):
        for inline in self.inline_instances:
            inline._parent_instance = obj
            yield inline.get_formset(request, obj)

class CarInline(TabularInline):
    _parent_instance = None

    def get_formset(self, *args, **kwargs):
        def formfield_callback(field, **kwargs):
            formfield = field.formfield(**kwargs)
            if field.name == 'car':
                formfield.queryset = Cars.objects.filter(owner=self._parent_instance)
            return formfield

        if self._parent_instance is not None:
            kwargs['formfield_callback'] = formfield_callback
        return super(CarInline, self).get_formset(*args,
                                                                 **kwargs)

Answer 2

我发现了一种更简单的方法，不需要在 get_formset() / get_formsets() / formfield_for_dbfield() 里搞来搞去。你可以使用 Django 的请求对象（你可以访问到这个对象），来获取 request.path_info，然后从 resolve 匹配的参数中获取主键（PK）。举个例子：

from django.contrib import admin
from django.core.urlresolvers import resolve
from app.models import YourParentModel, YourInlineModel


class YourInlineModelInline(admin.StackedInline):
    model = YourInlineModel

    def get_parent_object_from_request(self, request):
        """
        Returns the parent object from the request or None.

        Note that this only works for Inlines, because the `parent_model`
        is not available in the regular admin.ModelAdmin as an attribute.
        """
        resolved = resolve(request.path_info)
        if resolved.args:
            return self.parent_model.objects.get(pk=resolved.args[0])
        return None

    def has_add_permission(self, request):
        parent = self.get_parent_object_from_request(request)
        if parent and parent.is_active is True:
            return False
        return super(YourInlineModelInline, self).has_add_permission(request)

    def get_formset(self, request, *args, **kwargs):
        """
        Using the get_formset example from above to override the QuerySet.
        """
        def formfield_callback(field, **kwargs):
            formfield = field.formfield(**kwargs)
            if field.name == 'car':
                formfield.queryset = self.parent_model.objects.filter(
                    owner=self.get_parent_object_from_request(request)
                )
            return formfield

        if self.get_parent_object_from_request(request) is not None:
            kwargs['formfield_callback'] = formfield_callback

        return super(YourInlineModelInline, self).get_formset(*args, **kwargs)


@admin.register(YourParentModel)
class YourParentModelAdmin(admin.ModelAdmin):
    inlines = [YourInlineModelInline]

Answer 3

如果你很难从 request 中直接获取到 person，你可能需要通过重写 ModelAdmin.get_form() 或者 InlineModelAdmin.get_formset() 来手动传递它：

from functools import partial

class MyModelAdmin(admin.ModelAdmin):
    def get_form(self, request, obj=None, **kwargs):
        kwargs['formfield_callback'] = partial(self.formfield_for_dbfield, request=request, obj=obj)
        return super(MyModelAdmin, self).get_form(request, obj, **kwargs)

    def formfield_for_dbfield(self, db_field, **kwargs):
        person = kwargs.pop('obj', None)
        formfield = super(MyModelAdmin, self).formfield_for_dbfield(db_field, **kwargs)
        if db_field.name == "car" and person:
            formfield.queryset = Cars.objects.filter(owner=person)
        return formfield 

# or its inline
class MyInlineModelAdmin(admin.StackedInline):
    def get_formset(self, request, obj=None, **kwargs):
        kwargs['formfield_callback'] = partial(self.formfield_for_dbfield, request=request, obj=obj)
        return super(MyInlineModelAdmin, self).get_formset(request, obj, **kwargs)

    def formfield_for_dbfield(self, db_field, **kwargs):
        person = kwargs.pop('obj', None)
        formfield = super(MyInlineModelAdmin, self).formfield_for_dbfield(db_field, **kwargs)
        if db_field.name == "car" and person:
            formfield.queryset = Cars.objects.filter(owner=person)
        return formfield 

或者

class MyModelAdmin(admin.ModelAdmin):
    def get_form(self, request, obj=None, **kwargs):
        kwargs['formfield_callback'] = partial(self.formfield_for_dbfield, request=request, obj=obj)
        return super(MyModelAdmin, self).get_form(request, obj, **kwargs)

    def formfield_for_dbfield(self, db_field, **kwargs):
        if db_field.name != "car":
            kwargs.pop('obj', None)
        return super(MyModelAdmin, self).formfield_for_dbfield(db_field, **kwargs)

    def formfield_for_manytomany(self, db_field, request=None, **kwargs):
        person = kwargs.pop('obj', None)
        if db_field.name == "car" and person:
            kwargs['queryset'] = Cars.objects.filter(owner=person)
        return super(MyModelAdmin, self).formfield_for_manytomany(db_field, request, **kwargs)