4

My application configuration includes some values which need to be used in AR relationships. I'm aware this is an odd and potentially criminal thing to attempt, but I need to maintain the configuration as a textfile, and I honestly think I have a good case for a tableless model. Unfortunately I'm having trouble convincing AR (Rails 3.2) not to look for the table. My tableless model: 

class Tableless < ActiveRecord::Base

  def self.table_name
      self.name.tableize
  end

  def self.columns
    @columns ||= [];
  end

  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 self.columns_hash
    @columns_hash ||= Hash[columns.map { |column| [column.name, column] }]
  end

  def self.column_names
    @column_names ||= columns.map { |column| column.name }
  end

  def self.column_defaults
    @column_defaults ||= columns.map { |column| [column.name, nil] }.inject({}) { |m, e| m[e[0]] = e[1]; m }
  end

  def self.descends_from_active_record?
    return true
  end

  def persisted?
    return false
  end

  def save( opts = {} )
    options = { :validate => true }.merge(opts)
    options[:validate] ? valid? : true
  end
end

This is extended by the actual model: 

class Stuff < Tableless

  has_many :stuff_things
  has_many :things, :through => :stuff_things

  column :id, :integer
  column :name, :string
  column :value, :string

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

This is all based on code found here on SO and elsewhere, but alas, I get SQLException: no such table: stuffs: Any clues any one?

4

2 回答 2

3

对于 Rails >= 3.2，有activerecord-tableless gem。它是创建无表 ActiveRecord 模型的宝石，因此它支持验证、关联和类型。

当您在 Rails 3.x 中使用推荐的方式（使用 ActiveModel 而不是 ActiveRecord）时，不支持关联或类型。

于 2012-09-10T07:25:09.063 回答
1

对于 Rails >= 4，您还可以通过像这样定义无表类来获得对验证、关联和一些回调（如 after_initialize）的支持：

class Tableless < ActiveRecord::Base
    def self.columns() @columns ||= []; end

    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 

    attr_accessor :id, :name, :value

    has_many :stuff_things
    has_many :things, :through => :stuff_things

end
于 2015-08-05T13:53:10.640 回答