ruby-on-rails - Rails 多对多 SQLite3 错误

Question

我在 Rails 中创建了多对多关系，这是我的模型和迁移

class Channel < ActiveRecord::Base
  has_and_belongs_to_many :packages
  validates_presence_of :name
end

class Package < ActiveRecord::Base
  has_and_belongs_to_many :channels
  validates_presence_of :name
end

class CreateChannelsPackages < ActiveRecord::Migration
  def change
    create_table :channels_packages, :id => false do |t|
      t.references :channel
      t.references :package

      t.timestamps
    end
    add_index :channels_packages, :channel_id
    add_index :channels_packages, :package_id
  end
end

然后我有多个选择，但是当我尝试保存时出现此错误

SQLite3::ConstraintException: constraint failed: INSERT INTO "channels_packages" ("package_id", "channel_id") VALUES (1, 1)

我试图从迁移中删除索引但它没有解决它，其他人有这个问题吗？

顺便说一句，我正在使用 Rails 3.2.6 和 sqlite3 1.3.6

Answer 1

我不知道这是否是您的问题的原因，但是 has_and_belongs_to_many不推荐使用关联。

根据Rails Guide :

The use of extra attributes on the join table in a has_and_belongs_to_many association is deprecated. If you require this sort of complex behavior on the table that joins two models in a many-to-many relationship, you should use a has_many :through association instead of has_and_belongs_to_many.

我知道您没有向连接表添加任何额外的属性，但请尝试将迁移更改为以下内容，我认为是 default :

class CreateChannelPackageJoinTable < ActiveRecord::Migration
  def change
    create_table :channels_packages, :id => false do |t|
      t.integer :channel_id
      t.integer :package_id

      t.timestamps
    end
  end
end