[mongoid] How to extend mongoid model with new fields

I would do something like this:


module BasicUser
extend ActiveSupport::Concern

included do
field :username, type: String

field :title, type: String
end
end

class User
include Mongoid::Document
include BasicUser

field :signature, type: String
end

So you have a BasicUser module, and class User can include it.

Does store_in do what you want? http://mongoid.org/en/mongoid/docs/documents.html#storage

That way you'd have:

class User
include Mongoid::Document

field :username, type: String
field :title, type: String
end

class Myuser < User
store_in collection: 'myusers'

field :signature, type: String
field :picture, type: String
end

I've not used this myself but it looks like it would work.

James.

Your first solution will work just fine. Model inheritance works by putting
them all in the same collection.

Try out the code you have in solution 1, it'll work.

Thanks to all. But it is not quite what I want. Maybe I didn't specified it
good enough. All your cases are good for single inheritance. But what if n
people would like to contribute to a model. They would all have to be
synnchronized.

Example:
Class User1 < User
end
Class User2 < User1
end
Class UserN < UserN_1
end

What is not particular practical in praxis.

In big applications you often get cases where tables are extended by adding
another table to database and linked by id to main table.
Simple example:
Class User
end
Class User1
field: user_id
end
Class UserN
field: user_id
end
If you have list of all extensions, you can treat all tables as single
table. But in Mongo this can be much simpler, since it can be accomplished
in single record (document). The problem is just how to describe it with
Mongoid models.

by
TheR

I'm not sure what you mean by your statement in #1: "Is not ok since we get
new class and therefor new collection name. "

This is not true. When using inheritance, Mongoid stores all the documents
in the same collection, in your case "users". What would happen in your
case is that classes of type User would get stored in the "users"
collection with an additional field: "_type" => "User". MyUser documents
would have a "_type" => "MyUser" stored with it along with the additional
fields. Isn't this exactly what you want?

2013/1/2 TheR <[email protected]>

get new class and therefor new collection name. "

In this case you are correct. This is how mongoid behaves.
documents in the same collection, in your case "users". What would happen
in your case is that classes of type User would get stored in the "users"
collection with an additional field: "_type" => "User". MyUser documents
would have a "_type" => "MyUser" stored with it along with the additional
fields. Isn't this exactly what you want?

No. That would mean a new document for every model definition. What I would
like is that all fields from all definitions are saved to one document.


by
TheR


Dne četrtek, 03. januar 2013 10:23:05 UTC+1 je oseba Durran Jordan napisala:

Can you just post a gist of how you want the single document stored in the
database (the raw json or hash)? I think that would be easier to show you
how to model it.

2013/1/3 TheR <[email protected]>

class User
include Mongoid::Document

field :username, type: String
field :title, type: String
end

class MyUserExtension
extends_model :user # just my imagination

field :signature, type: String
field :picture, type: String
end

Would be stored to document as if I did only single declaration.

class User
include Mongoid::Document

field :username, type: String
field :title, type: String
field :signature, type: String
field :picture, type: String
end

I hope this is clear enough.

by
TheR


Dne četrtek, 03. januar 2013 11:36:10 UTC+1 je oseba Durran Jordan napisala:

Have u tried the solution i proposed . I guess it doest exaclty what u want.. Using include and concerns...

For extending single class.

Now imagine. You have working application and you would like to add
additional functionality. You provide that with a gem. You would like to
use existing user database, but need to add field to each document.

With AR, you would make a migration and field would be added to table
definition. But with mongoid all fields are defined inside model class. So
how to extend this model class.

by
TheR


Dne četrtek, 03. januar 2013 15:25:56 UTC+1 je oseba Arthur Neves napisala:

I decide to poke around source and I come out with this solution.

User::field :signature, type: String
User::belongs_to :visit
User::embeds_many :roles

Maybe just a little suggestion from my side, to make it little less ugly.

User::extend do
field :signature, type: String
belongs_to :visit
embeds_many :roles
end

by
TheR

A slightly cleaner approach is to put these in a module and then extend
User with the module.

module UserThing
field ...
end

User.extend UserThing

my first email in this thread shows the module solution ....

Indeed.

I think for a non-experienced Rubyist it's unusual to open up a class
post-definition, much less to pogrammatically extend it from another gem -
which is where the whole confusion came from. Your example, while
absolutely correct, didn't seem to answer TheR's question, it just needed
to say `User.extend BasicUser`.

I would use ActiveSupport::Concern as you suggest, too, just to keep things
more structurally organized.

a class post-definition, much less to pogrammatically extend it from
another gem - which is where the whole confusion came from. Your example,
while absolutely correct, didn't seem to answer TheR's question, it just
needed to say `User.extend BasicUser`.ail in this thread shows the module
solution ....

But it doesn't solve chicken egg problem ;-) In your example you define
extension class before it has to be included in basic class.

I wanted basic class to be fully defined and then extended sometime in
future without touching source code.
post-definition, much less to pogrammatically extend it from another gem -
which is where the whole confusion came from. Your example, while
absolutely correct, didn't seem to answer TheR's question, it just needed
to say `User.extend BasicUser`.

And now comes funny part. I didn't even know that extend exists in ruby
syntax and that it almost just does what I wanted. What I have written was
just a humble suggestion. Problem is in details. Extend can only extend
module not class. So this example throws error: wrong argument type Class
(expected Module)

class UserForForum # or module
extend User

field :signature, type: String
belongs_to :visit
embeds_many :roles
end


Can you please make a suggestion.

by
TheR

But it doesn't solve chicken egg problem ;-) In your example you define
extension class before it has to be included in basic class.

I wanted basic class to be fully defined and then extended sometime in
future without touching source code.


post-definition, much less to pogrammatically extend it from another gem -
which is where the whole confusion came from. Your example, while
absolutely correct, didn't seem to answer TheR's question, it just needed
to say `User.extend BasicUser`.

And now comes funny part. I didn't even know that extend exists in ruby
syntax and that it almost just does what I wanted. What I have written was
just a humble suggestion. Problem is in details. Extend can only extend
module not class. So this example throws error: wrong argument type Class
(expected Module)

class UserForForum # or module
extend User

field :signature, type: String
belongs_to :visit
embeds_many :roles
end


Can you please make a suggestion.

by
TheR