以编程方式创建组：无法从迁移访问权限 [英] Programmatically creating a group : Can't access permissions from migration

问题描述

在看到这篇文章后，我尝试通过此迁移在项目设置中创建自己的组：

After seeing this post, I tried to create my own group at project setup with this migration :

from django.db import migrations
from django.contrib.auth.models import Group, Permission

def create_group(apps, schema_editor):
    group, created = Group.objects.get_or_create(name='thing_managers')
    if created:
        add_thing = Permission.objects.get(codename='add_thing')
        group.permissions.add(add_thing)
        group.save()

class Migration(migrations.Migration):

    dependencies = [
        ('main', '0002_auto_20160720_1809'),
    ]

    operations = [
        migrations.RunPython(create_group),
    ]

但是我收到以下错误：

django.contrib.auth.models.DoesNotExist: Permission matching query does not exist.

这是我的模型：

class Thing(models.Model):
    pass

为什么我不能这样做？我如何解决这个问题？

Why can't I do that? How could I solve this?

我使用 django 1.9 。

推荐答案

权限是在 post_migrate 信号中创建的。在添加新模型后，首次迁移运行时不存在。运行 post_migrate可能是最简单的方法 信号处理程序手动：

Permissions are created in a post_migrate signal. They don't exist the first time migrations are run after a new model is added. It is probably easiest to run the post_migrate signal handler manually:

from django.contrib.auth.management import create_permissions

def create_group(apps, schema_editor):
    for app_config in apps.get_app_configs():
        create_permissions(app_config, apps=apps, verbosity=0)

    group, created = Group.objects.get_or_create(name='thing_managers')
    if created:
        add_thing = Permission.objects.get(codename='add_thing')
        group.permissions.add(add_thing)
        group.save()

create_permissions 检查现有权限，因此不会创建任何重复项。

create_permissions checks for existing permissions, so this won't create any duplicates.

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