Rails 3.2:从另一个迁移中调用\ down

Question

我想以类似于生成器的方式调用另一个迁移.基本上,如果您有一个创建表,那么在将来的某个时间点,您将不再使用该表,并且您希望迁移进行调用,up并且down与原始创建迁移的迁移完全相反.如果有可能那么我会创建一个类似的生成器

rails g reverse_migration CreateModel

然后结果是这样的

class ReverseCreateModel < ActiveRecord::Migration
  def up
    #call to create model down
  end
  def down
    #call to create model up
  end
end

我不想要任何解决方法,而是明确地重复代码并保持干净迁移和角色的能力.

任何帮助将不胜感激!

Answer 1

迁移只是一个Ruby文件,所以你可以require:

require "./db/migrate/20120117195557_create_model.rb"

class ReverseCreateModel < ActiveRecord::Migration
  def up
    CreateModel.new.down
  end

  def down
    CreateModel.new.up
  end
end

如果您的原始迁移使用change,则必须使用CreateModel.new.migrate(:down)和CreateModel.new.migrate(:up).

就我而言,migrate(direction)在迁移时使用时会产生更多输出:

==  ReverseCreateModel: migrating ======================================
==  CreateModel: reverting =============================================
(...)
==  CreateModel: reverted (0.0018s) ====================================

==  ReverseCreateModel: migrated (0.0019s) =============================

代替:

==  ReverseCreateModel: migrating ======================================
(...)
==  ReverseCreateModel: migrated (0.0019s) =============================

此答案基于/sf/answers/52802151/