Question

我需要从集合中删除相关实体。例如，我有M：N关系：项目有多个用户（用户可以有多个项目）。

如何从项目中删除用户，但不删除他？

# this removes user from project, but also deletes user
project.users.find(id: user._id).remove

由于

Answer 1

我们说我们有乐队，它有多个标签：

band = Band.all[1]
=> #<Band _id: 599d2c8a9d1fa2c5498024cc, name: "test_band", tag_ids: [BSON::ObjectId('599d2c8a9d1fa2c5498024cd'), BSON::ObjectId('599d2c8a9d1fa2c5498024ce'), BSON::ObjectId('599d2c8a9d1fa2c5498024cf')]>

然后，如果我们尝试删除一个相关的标记对象：

band.tags.delete(Tag.find(id: '599d2c8a9d1fa2c5498024cd')
...
MONGODB | localhost:27017 | test_development.update | SUCCEEDED | 0.000634s
=> #<Tag _id: 599d2c8a9d1fa2c5498024cd, name: "test_tag1", band_ids: []>

它将从band.tags数组中删除：

irb(main):088:0> band
=> #<Band _id: 599d2c8a9d1fa2c5498024cc, name: "test", tag_ids: [BSON::ObjectId('599d2c8a9d1fa2c5498024ce'), BSON::ObjectId('599d2c8a9d1fa2c5498024cf')]>

但该标签仍然作为对象存在：

Tag.find(id: '599d2c8a9d1fa2c5498024cd')
=> #<Tag _id: 599d2c8a9d1fa2c5498024cd, name: "test_tag1", band_ids: []>

Mongoid - 从M：N集合中删除实体但不删除它

1 个答案: