Rails5迁移：表没有用于的外键

Question

将我的Rails 4.2应用程序迁移到Rails 5后，当我尝试从新数据库迁移时，出现以下错误

表“目标”没有用于development_plan的外键

以下是重要的迁移：

1. 使用add_reference创建foreign_key

    class AddDevelopmentPlanToObjectives < ActiveRecord::Migration def change add_reference :objectives, :development_plan, index: true, foreign_key: true end end 

2. 删除外键（生成错误）

    class DropDevelopmentPlans < ActiveRecord::Migration def change Objective.all.each do |objective| company = objective.owner.company company.cycles.create name: '4Q 2015', begin_at: Date.today, end_at: 1.year.from_now, current: true unless company.current_cycle company.reload objective.update cycle: company.current_cycle end remove_foreign_key :objectives, :development_plan remove_reference :objectives, :development_plan, index: true drop_table :development_plans end end 

迁移在remove_foreign_key :objectives, :development_plan上中断

有人遇到这个问题吗？ 其他类似的迁移也会发生这种情况...

Answer 1

参考本文： https : //blog.bigbinary.com/2016/03/01/migrations-are-versioned-in-rails-5.html

Rails 5为迁移类添加了一个版本，因此：

在Rails 5.0中生成的迁移：

class CreateTasks < ActiveRecord::Migration[5.0]
 ...
end

如果没有，它将尝试为我们提供兼容性层。 虽然该兼容性层针对的是Rails 4.2，而那是根据该文章的默认值，但我会尝试将您的迁移更改为所有用途：

class AddDevelopmentPlanToObjectives < ActiveRecord::Migration[4.2]
  ....

看看是否有帮助。 如果没有，我将更改您的迁移以适应v5.0概述的更改

class AddDevelopmentPlanToObjectives < ActiveRecord::Migration[5.0]
  def change
    add_reference :objectives, :development_plan, foreign_key: true
  end
end

class DropDevelopmentPlans < ActiveRecord::Migration[5.0]
  def change
    Objective.all.each do |objective|
      company = objective.owner.company
      company.cycles.create name: '4Q 2015', begin_at: Date.today, end_at: 1.year.from_now, current: true unless company.current_cycle
      company.reload
      objective.update cycle: company.current_cycle
    end
    remove_foreign_key :objectives, :development_plan
    remove_reference :objectives, :development_plan
    drop_table :development_plans
  end
end

Answer 2

我相信to_table应该以复数形式倾斜：

remove_foreign_key :objectives, to_table: :development_plans

请参考rails api文档 。