我有以下 ActiveRecord 迁移:
class CreateSubjects < ActiveRecord::Migration
def self.up
create_table :subjects do |t|
t.string :title
t.timestamps
end
change_table :projects do |t|
t.references :subjects
end
end
def self.down
drop_table :subjects
remove_column :projects, :subjects_id #defeats the purpose of having references
end
end
我其实很喜欢这种references
风格。references
不幸的是,我在该self.down
部分中找不到等效的回滚。如果我写,remove_column :projects, :subjects_id
我也可以写t.integer :subjects_id
,这样会更安全。