Question

我有以下课程：

class Plugin(models.Model):
    pass 

class Instance(models.Model):
    plugins = models.ManyToManyField(Plugin, blank=True, null=True)

我的目标是编写一个cron作业，该作业从此实例获取插件列表以反映instance_plugin关系。 这意味着如果在现实生活中从实例中删除插件，则必须在此处反映。

for instance in Instance.objects.all():
    url = 'http://{}/wordpress_plugins'.format(instance.ip_address)
    ... 
    plugins = []
    for path, dic in response.json().items():
        plugin, created = Plugin.objects.update_or_create(
             ... 
        )
        plugins.add(plugin)

    instance.plugin_set = plugins

我正在TypeError: Direct assignment to the forward side of a many-to-many set is prohibited. Use plugins.set() instead.

我正在做的最好的方法是什么？

Answer 1

也许这可以做你想做的事如果您使用所有模型所具有的字段编辑代码，我可以为你提供一个更好的。

for instance in Instance.objects.all():
    url = 'http://{}/wordpress_plugins'.format(instance.ip_address)
    ... 
    plugins = []
    for path, dic in response.json().items():
        plugin, created = Plugin.objects.update_or_create(
            ... 
        )
        plugins.add(plugin)

    # First Option
    # We add each plugin from the Plugins List
    [instance.plugins.add(item) for item in plugins]
    # We loop through the instance to see which plugin is not in the New List Plugin, we delete it
    for plug in instance.plugins.all():
        if plug not in plugins:
            plug.delete()


    # 2nd Option
    # We clear the intance ManyToMany Field
    instance.plugins.clear()
    # We add each plugin from the Plugins List
    [instance.plugins.add(item) for item in plugins]
    # We loop The all The Plugin, to see which plugin does not have a reverse relation to instance
    for plug in Plugin.objects.all():
        if not plug.instance_set.all():
            plug.delete()

你如何保持ManyToMany关系的最新状态？

1 个答案: