Virtual model

Rails
1

Hello,

I would like to create a simple ActiveRecord model, but working without
table… Is that possible? I think we can this a virtual model.

And I would like to be able to use relations (like has_many :users, etc)
with this model (named App for instance), such as:

App.first.users

Thanks for any ideas.

2

If you are using rails 3, see this

3

yong gu wrote in post #957495:

If you are using rails 3, see this
#219 Active Model - RailsCasts

Thanks! But there is a problem with ActiveModel: I can not make
associations such as belongs_to or has_many…

4

I think if you use belongs_to or has_many, you must have to persist the
model. Or how can you retrieve the relationships

later?

5

Satsou Sa wrote in post #957508:

yong gu wrote in post #957495:

If you are using rails 3, see this
#219 Active Model - RailsCasts

Thanks! But there is a problem with ActiveModel: I can not make
associations such as belongs_to or has_many…

Why do you need them on a virtual model? Just write your own method.

belongs_to and has_many aren’t really useful if there’s no DB table, are
they? What are you trying to achieve?

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

6

Please quote when replying.

Satsou Sa wrote in post #957750:

Yes Marnen, I agree; it’s not really useful. But I prefer to do this
rather then having a table with only 1 row.

And you can.

That’s why I would like to
get a singleton model with a static data (and always the same id for
associations with other models).

Why do you need an ID? Again, please explain in more detail what you
are trying to do. has_many and belongs_to are only useful when dealing
with SQL, as I see it. Otherwise, you don’t need them; a non-SQL
approach could be as simple as

class Book < ActiveModel
attr_accessor :pages

def initialize
@pages = []
end
end
book = Book.new

…and then book.pages, book.pages.count, and book.pages << Page.new all
work as expected. That’s just the way OO development works.

has_many and belongs_to are a hack to make SQL databases feel more OO.
You don’t need them if there’s no SQL.

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

7

Yes Marnen, I agree; it’s not really useful. But I prefer to do this
rather then having a table with only 1 row. That’s why I would like to
get a singleton model with a static data (and always the same id for
associations with other models).