ruby-on-rails - 在 Ruby on Rails 3 中制作通用模型时出现问题

Question

我正在尝试制作一个“通用模型”，以便它可以连接到任何数据库的任何表。首先，我创建了这个连接到另一个指定数据库的类（不使用模式）

D b

class Db < ActiveRecord::Base

    self.abstract_class = true

    attr_accessor :error

    def initialize(item = nil)
        @error = ""
        connect
        super
    end

    def connect
        could_connect = true
        @error = ""

        begin
            ActiveRecord::Base.establish_connection(
              :adapter  => "mysql2",
              :host     => "localhost",
              :username => "root",
              :password => "",
              :database => "another_database", 
              :port => 3306,
              :encoding => "utf8"
            )
        rescue ActiveRecord::ConnectionNotEstablished
            @error = "Could not connect to database. The connection was not established"
            could_connect = false
        rescue Mysql2::Error
            @error = "Could not connect to database using MySQL2"
            could_connect = false
        rescue => e
            @error = "Could not connect to database. #{e.message}."
            could_connect = false
        end

        return could_connect
    end

end

然后，我创建了这个继承自 Db 并指定表名的类

模型

class Gmodel < Db

    def initialize(new_table_name)
        ActiveRecord::Base.set_table_name(new_table_name)
        super
    end

end

最后，在控制器中

主控制器

class MainController < ApplicationController

  def index
    @users = Gmodel.new("users")
  end

end

但是，它给了我这个错误：

undefined method `stringify_keys' for "users":String

有什么问题？有没有更好的方法来做到这一点？提前致谢！

Answer 1

为什么不简单地在运行时创建一个ActiveRecord::Base子类并避免所有麻烦呢？

t = 'some_table'
c = Class.new(ActiveRecord::Base) { self.table_name = t }

然后c引用一个 AR 类some_table，你可以做通常的事情：

o = c.find(1)
# 'o' is now a wrapper for the row of some_table where 'id = 1'

cols = c.columns.map(&:name)
# 'cols' is now an array of some_table's column names

这是 Ruby，其中类也是对象。

如果您需要连接到另一个数据库，那么您可以将establish_connection调用连同self.table_name：

t = 'some_table'
d = 'some_other_database'
c = Class.new(ActiveRecord::Base) do
    establish_connection(:adapter => 'mysql2', :database => d, ...)
    self.table_name = t
end