Rails 更新多对多记录

发布于 2024-10-20 17:29:36 字数 1269 浏览 4 评论 0原文

我在尝试更新现有的多对多记录时陷入困境。

项目模型：

class Project < ActiveRecord::Base
    belongs_to :assignment
    belongs_to :programmer
end

程序员模型：

class Programmer < ActiveRecord::Base
    has_many :projects
    has_many :assignments, :through => :projects
end

作业模型：

class Assignment < ActiveRecord::Base
    has_many :projects
    has_many :programmers, :through => :projects
end

所以我有这样链接的数据：

p = Programmer.create(:name => "Mike")

p.assignments.create(:name => "homework4")

p.assignments[0] = Assignment.find_or_create_by_name("homework1")

p.save

如您所见，我正在尝试将 Mike 的第一个硬件的关联更新为“homework1”。所有作业都已在作业表中，因此只需找到“homework1”并将其分配给 mike。不幸的是，当我输入第三行时没有错误，但它没有更新它。在内存中，p.assignments == homework1，但在数据库中它仍然是相同的（即使在 p.save 之后）。项目的连接表根本没有改变。

mysql 的日志显示每当我输入第三行时就会生成此命令。

SELECT "assignments".* FROM "assignments" WHERE "assignments"."name" = 'homework1' LIMIT 1

任何地方都没有更新......我做错了什么？

更新

所以我发现我可以直接引用联接表来编辑链接。大致如下：

proj = p.projects.first

proj.assignment_id = 12
proj.save!

原文

I'm getting stuck at trying to update an existing many to many record.

Project model:

class Project < ActiveRecord::Base
    belongs_to :assignment
    belongs_to :programmer
end

Programmer model:

class Programmer < ActiveRecord::Base
    has_many :projects
    has_many :assignments, :through => :projects
end

Assignment model:

class Assignment < ActiveRecord::Base
    has_many :projects
    has_many :programmers, :through => :projects
end

so I have data linked up like so:

p = Programmer.create(:name => "Mike")

p.assignments.create(:name => "homework4")

p.assignments[0] = Assignment.find_or_create_by_name("homework1")

p.save

so as you can see, I'm trying to update the association of Mike's first hw to "homework1". All the homework assignments are already in the assignments table so it shoud just find "homework1" and assign it to mike. unfortunately, when I type the third line there are no errors, but it doesn't update it. In memory, p.assignments == homework1, but in the DB it's still the same(even after p.save). The project's join table isn't changed at all.

the logs of mysql show this command being generated whenever I enter the 3rd line.

SELECT "assignments".* FROM "assignments" WHERE "assignments"."name" = 'homework1' LIMIT 1

there's no Update anywhere.... what am I doing wrong?

UPDATE

So I found out that I could just reference the join table directly to edit the links. Something along the lines of:

proj = p.projects.first

proj.assignment_id = 12
proj.save!

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稚然 2024-10-27 17:29:36

如果您只想引用该对象，那么您需要编辑迁移脚本 (db/migrate)。一个例子：

def self.up
  create_table :configurations do |t|
    t.string :name
    t.references :project  # This store just the id of the object.
    t.timestamps
  end
end

不要忘记输入：

rake db:migrate

If you just want a reference to the object, then you need to edit your migration scripts (db/migrate). An example:

def self.up
  create_table :configurations do |t|
    t.string :name
    t.references :project  # This store just the id of the object.
    t.timestamps
  end
end

Don't forget to type: