#219 Active Model

Very cool! I'd like to see more OM's in the NoSQL world to start using this, instead of cooking up their own!

Small caveat: ActiveModel defines before_validate and after_validate callbacks, but these aren't really usable: they're mixed up with the validations themselves, and invoked in the order they were defined. So, for example, if you declare a before_validate callback after a validates_presence_of, the before_validate will be called *after* the validation, which isn't very useful.

There's a change in edge now that moves before_validation and friends from ActiveRecord to ActiveModel to fix this, so expect that to make it to the release candidate.

Is it possible to just inherit from ActiveModel::Base?

If so, is there any good reason not to do this, instead of picking and choosing modules and having to dig through code to figure out which dependencies are missing?

Would also like response to dhc question. From some angles it looks like Rails 3 has a lot of features that come as a box of d-i-y components which you have to know how to assemble youself.

Surely this wasn't the point of Rails?

I think this is very dangerous...

send("#{name}=", value)

instead of including ActiveModel::Conversion module, extending ActiveModel::Naming module, and defining the persisted? method...

Another option would have been to change the form_for call in the view. Just change "form_for @message" to "form_for :message, :url => messages_path"

@jonas, why? Rails does this in a similar way. Except all it does is check for protected attributes that shouldn't be mass assigned first and that the object responds to "#{key}=". If you want to add your own ability to have protected attributes, then go for it. I just don't think that's in the scope of this railscast.

http://github.com/rails/rails/blob/master/activerecord/lib/active_record/base.rb#L1532

Just an idea, totally unrelated to the screencast.
You could make a good use of p2p and give torrent links among with the usual download links.

@dhc (Since people are asking): You could define an "ActiveModel::Base" class and include the functionality you want for your app. The nice thing about the modular architecture is that you can do exactly what you are looking to do, but it's not forced upon you. So just define your own base class and include the modules you want for all of your inheriting classes. Don't get this confused with ActiveRecord, as that a different set of classes and modules, that happen to leverage the ActiveModel classes/modules.

Very nice screencast, Ryan! I had the same problem with ActiveRecord on rails 2 which requires some hacks in order to make the model not db specific. Great work on introducing ActiveModel! You mentioned downloading the rails 3 codes and read it. I just found out a neat tool that makes it easier to read codes from a source control system on your browser, it's called CodeFaces, here is the restful link to read the rails code on GitHub: http://codefaces.org/http://github.com/rails/rails

I made a gem called basic_model, based on this approach:

http://github.com/petebrowne/basic_model
http://rubygems.org/gems/basic_model

Anyone using serializers? I can't get them to work. Active Model is great but need some more polishing in my opinion.

Is it possible to use formtastic's semantic_form_for with a tableless model? Without using the Tableless gem?

It would be good to have an episode on tableless models with MongoID!

Hi Ryan,

Thanks again for the Railscast.

I'm upgrading our Rails 2.3.11 app straight to 3.1 and my old tableless models don't work anymore (as per screencast #193). This stuff in this railscast looks nice and clean but I'm a little confused why no one else is coming up against the problem of no longer getting access to associations and the SQL Column benefits of the old way.

We use things like:

column :option, :string, "Default"

and

has_many :areas
accepts_nested_attributes_for :areas

Is there some ActiveRecord goodness we can include/extend?

If not, the actual problem we have is that as of Rails 3.1 the tableless models are trying to hit the DB looking for "tablelesses" when initializing etc.

Thanks,
Matt

Hi all,

I've had a few people ask, just so you know I ended up having to implement Tableless like this to get it going with Rails 3.1 and working with associations.

Put this in your app/models dir and then extend it to get a tableless model that still supports all the associations like has_many, belongs_to etc, validations and basically smells like a real model.

We use it a fair bit for things like filter models, giving us very clean view and controller code.

https://gist.github.com/1101257

Enjoy.
//matt

This is great! So I created a model and I am having a separate issue. Since I use the @errors = ActiveModel::Errors.new(self) collection in my initializer and validators, when I generate JSON to store in my NOSQL database, it's including all kinds of stuff that I don't want to store:

{"errors"=>#, @username="jasdeep", @validation_context=nil, @firstname="Jasdeep", @lastname="Jaitla", @messages={}>, "username"=>"jasdeep", "email"=>... and so on

I've tried calling:

@user.as_json(only: [ :username, :email, :firstname, :lastname ])

as recommended in: api.rubyonrails.org -- ActiveModel::Serializers::JSON

but it has no effect, it still outputs every attribute and object. I have looked EVERYWHERE googling for hours upon hours and still can't find a solution for this.

I've tried overriding as_json in my Model class, but still no effect.

Any help or pointers are appreciated...

class User

include ActiveModel::Validations
include ActiveModel::Conversion
include ActiveModel::Serialization
extend ActiveModel::Callbacks
extend ActiveModel::Naming

attr_accessor :username, :email, :password, ... etc

def as_json(options={})
super(:only => [:username, :email])
end

Thanks!

Rails/ActiveModel 3.2.1
Ruby 1.9.3.p0

Hey!

Following the activemodel source code, the initialize method should check if the attributes isn't nil.

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

Without it, I got errors running my specs

 NoMethodError:
   undefined method `each' for nil:NilClass

Anyone trying translating ? I tried this, as mentioned in API docs:

http://api.rubyonrails.org/classes/ActiveModel/Translation.html

class TranslatedPerson
  extend ActiveModel::Translation
end

Actually what I am trying to do is translate the error messages. The message part like "can not be empty", etc. worked, but the attribute names still in english.

Hi There, thanks for the rail cast I am wondering if anyone has had experience with using these in multi step forms like that of the #217 Rails Cast as it would be better if I could do this without the Active Record database creation, as well as possibly removing the sessions to be used in memcache instead, it seems there isn't a lot of info on this and would be very appreciative for any help someone can offer!

Any idea on how to test the mailer for the contact form in Rails 4?

Hi ryan,

thanks for your article.

How to make pre-populate on the form?
Because currently My form always did not pre-populate.

Thanks

Hmm, nice. I'd like to know how I can keep on using belongs_to though. My tableless model is actually connected to ActiveRecord models, as in episode 193 with articles.

Any new way to do this with rails 4 for instance ?

Hi,
if i have

attr_accessor :date, :count 

where :date is a datetime and :count is a integer, i have this error "NoMethodError (undefined method `data(1i)=' for".

Can i declare :date as a datetime?

Please note the new ActiveModel::Model available in Rails 4 which makes it much easier to create a tableless model. In fact, the code shown in this screencast for the model doesn't actually work fully with Rails 4 presumably because of this change (at least it didn't work for me). For info, see: http://blog.plataformatec.com.br/2012/03/barebone-models-to-use-with-actionpack-in-rails-4-0/

One comment: the persisted? public instance method defaults to return false.

How i can get error messages when validation fails. Please someone help me to fix this. Any help will be appreciated. Thanks

nothing