CODEWITHSUNDEEP
ruby-on-railsactiverecordmodel
John Schulze
John Schulze

Reputation: 2198

Tableless model with ActiveRecord associations in Rails 3.2

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?

Upvotes: 4

Views: 4446

Answers (2)

Eric
Eric

Reputation: 3792

For Rails >= 4 you can also get support for validations, associations, and some callbacks (like after_initialize) by defining your tableless classes like this:

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

Upvotes: 1

Jarl
Jarl

Reputation: 2861

For Rails >= 3.2 there is the activerecord-tableless gem. Its a gem to create tableless ActiveRecord models, so it has support for validations, associations, types.

When you are using the recommended way (using ActiveModel opposed to ActiveRecord) to do it in Rails 3.x there is no support for association nor types.

Upvotes: 3

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