A "related manager" is a manager used in a one-to-many or many-to-many\nrelated context. This happens in two cases:
\nThe "other side" of a ForeignKey relation.\nThat is:
from django.db import models\n\nclass Reporter(models.Model):\n # ...\n pass\n\nclass Article(models.Model):\n reporter = models.ForeignKey(Reporter, on_delete=models.CASCADE)\nIn the above example, the methods below will be available on\nthe manager reporter.article_set.
Both sides of a ManyToManyField relation:
class Topping(models.Model):\n # ...\n pass\n\nclass Pizza(models.Model):\n toppings = models.ManyToManyField(Topping)\nIn this example, the methods below will be available both on\ntopping.pizza_set and on pizza.toppings.
Adds the specified model objects to the related object set.
\n実装例:
\n>>> b = Blog.objects.get(id=1)\n>>> e = Entry.objects.get(id=234)\n>>> b.entry_set.add(e) # Associates Entry e with Blog b.\nIn the example above, in the case of a\nForeignKey relationship,\nQuerySet.update()\nis used to perform the update. This requires the objects to already be\nsaved.
You can use the bulk=False argument to instead have the related\nmanager perform the update by calling e.save().
Using add() with a many-to-many relationship, however, will not\ncall any save() methods, but rather create the relationships\nusing QuerySet.bulk_create(). If you need to execute\nsome custom logic when a relationship is created, listen to the\nm2m_changed signal.
Creates a new object, saves it and puts it in the related object set.\nReturns the newly created object:
\n>>> b = Blog.objects.get(id=1)\n>>> e = b.entry_set.create(\n... headline='Hello',\n... body_text='Hi',\n... pub_date=datetime.date(2005, 1, 1)\n... )\n\n# No need to call e.save() at this point -- it's already been saved.\nThis is equivalent to (but much simpler than):
\n>>> b = Blog.objects.get(id=1)\n>>> e = Entry(\n... blog=b,\n... headline='Hello',\n... body_text='Hi',\n... pub_date=datetime.date(2005, 1, 1)\n... )\n>>> e.save(force_insert=True)\nNote that there's no need to specify the keyword argument of the model\nthat defines the relationship. In the above example, we don't pass the\nparameter blog to create(). Django figures out that the new\nEntry object's blog field should be set to b.
Removes the specified model objects from the related object set:
\n>>> b = Blog.objects.get(id=1)\n>>> e = Entry.objects.get(id=234)\n>>> b.entry_set.remove(e) # Disassociates Entry e from Blog b.\nSimilar to add(), e.save() is called in the example above\nto perform the update. Using remove() with a many-to-many\nrelationship, however, will delete the relationships using\nQuerySet.delete() which\nmeans no model save() methods are called; listen to the\nm2m_changed signal if you wish to\nexecute custom code when a relationship is deleted.
For ForeignKey objects, this method only\nexists if null=True. If the related field can't be set to None\n(NULL), then an object can't be removed from a relation without\nbeing added to another. In the above example, removing e from\nb.entry_set() is equivalent to doing e.blog = None, and because\nthe blog ForeignKey doesn't have\nnull=True, this is invalid.
For ForeignKey objects, this method accepts\na bulk argument to control how to perform the operation.\nIf True (the default), QuerySet.update() is used.\nIf bulk=False, the save() method of each individual model\ninstance is called instead. This triggers the\npre_save and\npost_save signals and comes at the\nexpense of performance.
Removes all objects from the related object set:
\n>>> b = Blog.objects.get(id=1)\n>>> b.entry_set.clear()\nNote this doesn't delete the related objects -- it just disassociates\nthem.
\nJust like remove(), clear() is only available on\nForeignKeys where null=True and it also\naccepts the bulk keyword argument.
Replace the set of related objects:
\n>>> new_list = [obj1, obj2, obj3]\n>>> e.related_set.set(new_list)\nThis method accepts a clear argument to control how to perform the\noperation. If False (the default), the elements missing from the\nnew set are removed using remove() and only the new ones are added.\nIf clear=True, the clear() method is called instead and the\nwhole set is added at once.
The bulk argument is passed on to add().
Note that since set() is a compound operation, it is subject to\nrace conditions. For instance, new objects may be added to the database\nin between the call to clear() and the call to add().
A related object set can be replaced in bulk with one operation by assigning a\nnew iterable of objects to it:
\n>>> new_list = [obj1, obj2, obj3]\n>>> e.related_set = new_list\nIf the foreign key relationship has null=True, then the related manager\nwill first disassociate any existing objects in the related set before adding\nthe contents of new_list. Otherwise the objects in new_list will be\nadded to the existing related object set.