django 插入库表时如何添加many-to-many字段数据
Posted Jason_WangYing
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创建对象时，多对多字段不能直接通过下面的方式处理:
from .models import Blog, Author, User
author = Author.objects.get(id=1)
users = User.objects.filter(id__in=(2, 3, 4))
# 这样直接写过不了，会报错: Direct assignment to the forward side of a many-to-many set is prohibited
Blog.objects.create(
author=author,
likes=users
)会报错：TypeError: Direct assignment to the forward side of a many-to-many set is prohibited
在创建表时就添加多对多数据的话，可通过下面的方式来处理：
from .models import Blog, Author, User
author = Author.objects.get(id=1)
users = User.objects.filter(id__in=(2, 3, 4))
# 这样直接写过不了，会报错: Direct assignment to the forward side of a many-to-many set is prohibited
blog = Blog.objects.create(
author=author
)
# create的时候不写many to many 字段，写完后单独设置这些字段就可以了
blog.likes.set(users)如果报错：ValueError: “needs to have a value for field ”id“ before this many-to-many relationship can be used”
from .models import Blog, Author, User
author = Author.objects.get(id=1)
users = User.objects.filter(id__in=(2, 3, 4))
# 这样直接写过不了，会报错: Direct assignment to the forward side of a many-to-many set is prohibited
blog = Blog(
author=author
)
# create的时候不写many to many 字段，写完后单独设置这些字段就可以了
blog.likes.set(users)这是由于没有用create来创建，直接用Bolg来创建了，正确的是下面
from .models import Blog, Author, User
author = Author.objects.get(id=1)
users = User.objects.filter(id__in=(2, 3, 4))
# 这样直接写过不了，会报错: Direct assignment to the forward side of a many-to-many set is prohibited
blog = Blog.objects.create(
author=author
)
# create的时候不写many to many 字段，写完后单独设置这些字段就可以了
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