Ruby on Rails的：全功能无表格模型 [英] Ruby on Rails: Fully functional tableless model

问题描述

寻找一个无表格的典范后，我碰到这个code这似乎是对如何创建一个普遍的共识。

After searching for a tableless model example I came across this code which seems to be the general consensus on how to create one.

class Item < ActiveRecord::Base
class_inheritable_accessor :columns
  self.columns = []

  def self.column(name, sql_type = nil, default = nil, null = true)
    columns << ActiveRecord::ConnectionAdapters::Column.new(name.to_s, default, sql_type.to_s, null)
  end

  def all
    return []
  end

  column :recommendable_type, :string
  #Other columns, validations and relations etc...
end

不过我也喜欢它的功能，作为一种模式呢，再presenting对象的集合，这样我可以做Item.all。

However I would also like it to function, as a model does, representing a collection of object, so that I can do Item.all.

该计划是为了填充文件的项目，每个项目的属性会从文件中提取的。

The plan is to populate Items with files and each Item's properties will be extracted from the files.

不过现在如果我这样做Item.all我收到了

However currently if I do Item.all I get a

Mysql2 ::错误表test_dev.items不存在...

错误。

推荐答案

我找到了一个例子，在<一个href="http://railscasts.com/episodes/219-active-model">http://railscasts.com/episodes/219-active-model在那里我可以用模型特征，然后覆盖静态方法都一样（之前应该已经想到了这一点）。

I found an example at http://railscasts.com/episodes/219-active-model where I can use model features and then override static methods like all (should have thought of this before).

class Item
  include ActiveModel::Validations
  include ActiveModel::Conversion
  extend ActiveModel::Naming

  attr_accessor :name, :email, :content

  validates_presence_of :name
  validates_format_of :email, :with => /^[-a-z0-9_+\.]+\@([-a-z0-9]+\.)+[a-z0-9]{2,4}$/i
  validates_length_of :content, :maximum => 500

  class << self
    def all
      return []
    end
  end

  def initialize(attributes = {})
    attributes.each do |name, value|
      send("#{name}=", value)
    end
  end

  def persisted?
    false
  end
end

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