Question

我的车队管理rails app有两种型号

class Location < ActiveRecord::Base
  has_many :fleets
end

class Fleet < ActiveRecord::Base
  belongs_to :location
end

fleets表的location_id为外键，state列表示fleet的状态（active，inactive，new）。现在我想编写迁移以将此关系移动到名为Allotment的第三个模型中。我的模型看起来应该是这样的

class Location < ActiveRecord::Base
  has_many :allotments
  has_many :fleets, :through => :allotments
end
class Fleet < ActiveRecord::Base
  has_many :allotments
  has_many :branches, :through => :allotments
end
class Allotment < ActiveRecord::Base
  belongs_to :fleet
  belongs_to :location
end

将迁移编写到 -

的最佳方法是什么

从location_id中删除外键fleets并同时填充allotments表中的记录。
将state列从fleets移至allotments并填充
如何在不破坏代码的情况下使这些迁移可逆。

如下编写迁移是否合适？或者我应该编写两个单独的迁移，一个用于创建allotments并填充它，另一个用于从fleets删除列？我错过了以下迁移中的任何重要内容吗？

def self.up 
  create_table :allotments do |t|
    t.references :fleet, index: true
    t.references :location, index: true
    t.string :state
  end
  Fleet.all.each do |f|
    l = f.location
    Allotment.create(fleet: f, location: l, state: f.state)
  end
  remove_reference :fleets, :location, index: true
  remove_column :fleets, :state
end 
self.down
  add_refrence :fleets, :location, index: true
  add_column :fleets, :state, :string
  Fleet.all.each do |f|
    f.update_column :state, f.allotments.first.state
    f.update_column :location_id, f.locations.first.id
  end
  drop_table :allotments
end

rails migration将外键移动到第三个连接模型

0 个答案: