Ruby on Rails 3 (3.1) ActiveModel Associations (tableless nested models)

Question

How to impliment ActiveModel associations (tableless nested models)?

For example:

book has many chapters

With ActiveRecord I would create two models and assosiate them with has_many and belongs_to. But ActiveModel doesn't have such functionality. How can I implement this?

Jarl · Answer 1 · 2013-10-04T06:36:34.097

7

With rails versions >= 2.3.x you can use the activerecord-tableless gem. With that gem you can have associations and validations without a database.

Update

I have been added as author to the gem and I have updated the gem to support newer Rails versions. So now we can have tableless models with associations in Rails versions >= 2.3

edited Oct 04 '13 at 06:36

answered Aug 05 '11 at 10:07

Jarl

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@Tilo you probably already figured out but... You can use `ActiveModel::Model` http://api.rubyonrails.org/classes/ActiveModel/Model.html – nandilugio Nov 18 '14 at 14:56

score 5 · Accepted Answer · answered Jul 06 '11 at 08:59

5

You simply can't do it that way. It is not active record.

You can check ActiveModel documentation (and source code) at :

https://github.com/rails/rails/tree/master/activemodel

I guess you have to do it old fashion way, using an array of chapters and a reference to the book in the chapters.

Hope this helps!

answered Jul 06 '11 at 08:59

Dominic Goulet

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Thank you for your response, Dominic. I'm new to Ruby language, can you explain what you mean by saying "a reference to the book in the chapters"? – WHITECOLOR Jul 06 '11 at 09:37
Happy I helped! So : Your "chapter" class should have a "book" member which you would affect to the actual "book" that the "chapter" is in. In the "book" class, add an array of all the "chapters" that the book contains. – Dominic Goulet Jul 06 '11 at 14:49

score 0 · Answer 3 · edited May 23 '17 at 12:06

You can check out this answer for another way to do it.

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

Ruby on Rails 3 (3.1) ActiveModel Associations (tableless nested models)

3 Answers3

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