Question

我想将错误的变量名更改为新变量，因此我创建了真实和新变量，但旧的和错误的变量仍然存在！

如何删除假的

irb(main):001:0> item = Item.last Item Load (0.3ms) SELECT "items".* FROM "items" ORDER BY "items"."id" DESC LIMIT ? [["LIMIT", 1]] => #<Item id: 6, title: "Make a cake for your darling", description: "She loves furit ", created_at: "2019-02-27 18:04:15", updated_at: "2019-02-27 18:04:15", user_id: 2, complated_at: nil, completed_at: nil> irb(main):002:0>

我错了一个错字，必须“完整”

我该怎么办？

Answer 1

rails g migration remove_complated_at_from_items complated_at:datetime

此行生成这些代码

class RemoveComplatedAtFromItems < ActiveRecord::Migration[5.2]
  def change
    remove_column :items, :complated_at, :datetime
  end
end

我当前的schema.rb文件

ActiveRecord::Schema.define(version: 2019_02_27_204841) do
  create_table "items", force: :cascade do |t|
    t.string "title"
    t.text "description"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "user_id"
    t.datetime "completed_at"
    t.datetime "complated_at"
  end

现在让我们运行rails db：migrate

$ rails db:migrate

== 20190227204841 RemoveComplatedAtFromItems: migrating =======================
-- remove_column(:items, :complated_at, :datetime)
   -> 0.0038s
== 20190227204841 RemoveComplatedAtFromItems: migrated (0.0039s) ==============

似乎一切都还好！让我们检查一下schema.rb！

ActiveRecord::Schema.define(version: 2019_02_27_204841) do
  create_table "items", force: :cascade do |t|
    t.string "title"
    t.text "description"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "user_id"
    t.datetime "completed_at"
  end

现在一切都很好。从左至左检查一个对象！

 rails c
irb(main):001:0> item = Item.last
  Item Load (0.3ms)  SELECT  "items".* FROM "items" ORDER BY "items"."id" DESC LIMIT ?  [["LIMIT", 1]]
=> #<Item id: 6, title: "Make a cake for your darling", description: "She loves furit ", created_at: "2019-02-27 18:04:15", updated_at: "2019-02-27 18:04:15", user_id: 2, completed_at: nil>

完成！

Answer 2

创建迁移并使用remove_column方法来更改数据库。

https://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-remove_column

Answer 3

不删除列。只需重命名即可。

创建一个新的迁移并放入代码：

rename_column :items, :complated_at, :completed_at

如何在Rails上的ruby上更改模型属性名称

3 个答案: