Ruby-on-rails Rails 迁移：t.references 具有替代名称？
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Rails migration: t.references with alternative name?
提问by themirror
So I have a create_table like this for Courses at a School:
所以我有一个像这样的学校课程的 create_table ：
create_table :courses do |t|
t.string :name
t.references :course
t.timestamps
end
but I want it to reference twoother courses like:
但我想它引用2门其他课程，如：
has_many :transferrable_as # A Course
has_many :same_as # Another Course
Can I say the following?
我可以说以下吗？
t.references :transferrable_as, :as=> :course
采纳答案by themirror
I think this thread has a different more Rails-ish way: Scaffolding ActiveRecord: two columns of the same data type
我认为这个线程有一个不同的更 Rails 的方式： Scaffolding ActiveRecord: two columns of the same data type
In the migration:
在迁移中：
t.belongs_to :transferrable_as
t.belongs_to :same_as
t.belongs_to :transferrable_as
t.belongs_to :same_as
回答by Ryan
You can do this all in the initial migration/column definition (at least currently in Rails 5):
您可以在初始迁移/列定义中完成这一切（至少目前在 Rails 5 中）：
t.references :transferable_as, index: true, foreign_key: {to_table: :courses}
t.references :same_as, index: true, foreign_key: {to_table: :courses}
回答by Toby 1 Kenobi
You can do it this way:
你可以这样做：
create_table :courses do |t|
t.string :name
t.references :transferrable_as, references: :courses
t.references :same_as, references: :courses
t.timestamps
end
or using t.belongs_toas an alias for t.references
或t.belongs_to用作别名t.references
You can't add foreign_key: trueto those two references lines. If you want to mark them as foreign keys at the database level you need to have a migration with this:
您不能添加foreign_key: true到这两个参考行。如果您想在数据库级别将它们标记为外键，您需要进行迁移：
add_foreign_key :courses, :courses, column: :transferrable_as_id
add_foreign_key :courses, :courses, column: :same_as_id
Update
更新
In Rails 5.1 and above you can add the foreign key in the migration in the create_tableblock like this:
在 Rails 5.1 及更高版本中，您可以在create_table块中的迁移中添加外键，如下所示：
create_table :courses do |t|
t.string :name
t.references :transferrable_as, foreign_key: { to_table: 'courses' }
t.references :same_as, foreign_key: { to_table: 'courses' }
t.timestamps
end
回答by Diego Diaz de Berenguer
As an added answer to this question -- the Model should have the following line to complete the association:
作为对这个问题的补充回答——模型应该有以下行来完成关联：
belongs_to :transferrable_as, class_name: "Course"
belongs_to :same_as, class_name: "Course"
回答by Ju Nogueira
I don't think referencesaccepts the :asoption, but you can create your columns manually...
我认为不references接受该:as选项，但您可以手动创建列...
create_table :courses do |t|
t.string :name
t.integer :course1_id
t.integer :course2_id
t.timestamps
end
