ruby-on-rails - “：first”迁移参数不起作用？

Question

我想添加一个新列：

class AddNameToUsers < ActiveRecord::Migration
  def change
    add_column :users, :name, :string, :first => true
  end
end

:first我包含了将列放在所有其他列之前的论点。但似乎没有用：

create_table "users", :force => true do |t|
    t.string   "email",                  :default => "", :null => false
    t.string   "encrypted_password",     :default => "", :null => false
    t.string   "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.integer  "sign_in_count",          :default => 0
    t.datetime "current_sign_in_at"
    t.datetime "last_sign_in_at"
    t.string   "current_sign_in_ip"
    t.string   "last_sign_in_ip"
    t.string   "name"
  end

难道我做错了什么？

Answer 1

我们无法使用迁移文件来实现这一点。但我们可以做以下事情..

     ActiveRecord::ConnectionAdapters::MysqlAdapter.class_eval do
     def add_column_options!(sql, options)
     super
     if options[:after]
     sql << " AFTER #{quote_column_name(options[:after])}"
     elsif options[:first]
     sql << " FIRST"
     end
     end
     end

     So now

     a.add_column :users, :name, :string, :after => "baz"

      will execute

      ALTER TABLE `users` ADD `name` varchar(20)  AFTER `baz`

      and

      a.add_column :users, :name, :string, :first => true

      will execute

      ALTER TABLE `users` ADD `name` varchar(20)  FIRST

      Likewise for change_column.