Ruby on rails 未定义方法的挂起迁移错误-Rails 4

我正在修复将数据库表中的列类型从整数命名为datetime时出错的问题。但是，在我运行rake db:migrate之后，我得到了一个挂起的迁移错误。当我通过rails g MigrateDeliveryTimeDates添加新的迁移时，db/migrate下没有生成新文件，所以我手动创建了它。错误内容如下：

An error has occurred, this and all later migrations canceled:
undefined method `deliverytime_temp'

这是我的db/migrate文件：

class ChangeColumnDeliveryTime < ActiveRecord::Migration
  def change
    rename_column(:deliveries, :deliverytime, :deliverytime_temp)
    add_column(:deliveries, :deliverytime, :datetime)  
  end
end

如何解决此错误？

您需要使用方法来代替

def change
  # rename_column :table_name, :old_column_name, :new_column_name
  rename_column :deliveries, :deliverytime, :deliverytime_temp
  change_column :deliveries, :deliverytime_temp, :datetime
  # change_column :table_name, :column_name, :new_data_type
end

---

当我进行这些建议的更改、保存并运行rake db:migrate时，仍然会出现以下错误：“雷克！StandardError:发生错误，此迁移和所有后续迁移已取消：#@Codestudio:确定的未定义方法'deliverytime_temp'，然后将

change\u列：deliveries，：deliverytime，：datetime

放在

rename\u coulmn

之前，同时删除

ChangeColumnDeliveryTime

迁移文件

ActiveRecord::Schema.define(version: 20160216220012) do

  create_table "deliveries", force: :cascade do |t|
    t.string   "name"
    t.string   "deliveryaddress"
    t.integer  "deliverytime"
    t.string   "notes"
    t.integer  "order_id"
    t.datetime "created_at",      null: false
    t.datetime "updated_at",      null: false
  end

  add_index "deliveries", ["order_id"], name: "index_deliveries_on_order_id"

  create_table "orders", force: :cascade do |t|
   t.datetime "date"
   t.string   "name"
   t.string   "pickup"
   t.datetime "pickuptime"
   t.datetime "created_at", null: false
   t.datetime "updated_at", null: false
  end
end

def change
  # rename_column :table_name, :old_column_name, :new_column_name
  rename_column :deliveries, :deliverytime, :deliverytime_temp
  change_column :deliveries, :deliverytime_temp, :datetime
  # change_column :table_name, :column_name, :new_data_type
end