Is it possible to create form for simple class - ruby-on-rails

Question

I just want to have ablility to edit class properties whish is not successor of ActiveRecord class.
Here is my class /app/model/entry.rb:
class Entry
attr_accessor :title, :body
end
Here is a controller:
class DiaryController < ApplicationController
def new
#entry = Entry.new
end
end
Here is a view:
<%= form_for(#entry) do |f| %>
<%= f.text_field :title %> <br />
<%= f.text_area :body %> <br />
<% end %>
I got the error message while I was opening form:
undefined method `model_name' for Entry:Class
Here is full stack:
Extracted source (around line #1):
1: <%= form_for(#entry) do |f| %>
2: <%= f.text_field :title %> <br />
3: <%= f.text_area :body %> <br />
4: <% end %>
Full trace:
activemodel (3.0.6) lib/active_model/naming.rb:95:in `model_name_from_record_or_class'
activemodel (3.0.6) lib/active_model/naming.rb:82:in `singular'
actionpack (3.0.6) lib/action_view/helpers/form_helper.rb:312:in `form_for'
app/views/diary/new.html.erb:1:in `_app_views_diary_new_html_erb___902027577_26033568_187052521'
actionpack (3.0.6) lib/action_view/template.rb:135:in `block in render'
activesupport (3.0.6) lib/active_support/notifications.rb:54:in `instrument'
actionpack (3.0.6) lib/action_view/template.rb:127:in `render'
actionpack (3.0.6) lib/action_view/render/rendering.rb:59:in `block in _render_template'
activesupport (3.0.6) lib/active_support/notifications.rb:52:in `block in instrument'
activesupport (3.0.6) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.0.6) lib/active_support/notifications.rb:52:in `instrument'
actionpack (3.0.6) lib/action_view/render/rendering.rb:56:in `_render_template'
actionpack (3.0.6) lib/action_view/render/rendering.rb:26:in `render'
actionpack (3.0.6) lib/abstract_controller/rendering.rb:115:in `_render_template'
actionpack (3.0.6) lib/abstract_controller/rendering.rb:109:in `render_to_body'
actionpack (3.0.6) lib/action_controller/metal/renderers.rb:47:in `render_to_body'
actionpack (3.0.6) lib/action_controller/metal/compatibility.rb:55:in `render_to_body'
actionpack (3.0.6) lib/abstract_controller/rendering.rb:102:in `render_to_string'
actionpack (3.0.6) lib/abstract_controller/rendering.rb:93:in `render'
actionpack (3.0.6) lib/action_controller/metal/rendering.rb:17:in `render'
actionpack (3.0.6) lib/action_controller/metal/instrumentation.rb:40:in `block (2 levels) in render'
activesupport (3.0.6) lib/active_support/core_ext/benchmark.rb:5:in `block in ms'
c:/Ruby192/lib/ruby/1.9.1/benchmark.rb:309:in `realtime'
activesupport (3.0.6) lib/active_support/core_ext/benchmark.rb:5:in `ms'
actionpack (3.0.6) lib/action_controller/metal/instrumentation.rb:40:in `block in render'
actionpack (3.0.6) lib/action_controller/metal/instrumentation.rb:78:in `cleanup_view_runtime'
activerecord (3.0.6) lib/active_record/railties/controller_runtime.rb:15:in `cleanup_view_runtime'
actionpack (3.0.6) lib/action_controller/metal/instrumentation.rb:39:in `render'
actionpack (3.0.6) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (3.0.6) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
actionpack (3.0.6) lib/abstract_controller/base.rb:150:in `process_action'
actionpack (3.0.6) lib/action_controller/metal/rendering.rb:11:in `process_action'
actionpack (3.0.6) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.0.6) lib/active_support/callbacks.rb:436:in `_run__776311234__process_action__123531476__callbacks'
activesupport (3.0.6) lib/active_support/callbacks.rb:410:in `_run_process_action_callbacks'
activesupport (3.0.6) lib/active_support/callbacks.rb:94:in `run_callbacks'
actionpack (3.0.6) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.0.6) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.0.6) lib/active_support/notifications.rb:52:in `block in instrument'
activesupport (3.0.6) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.0.6) lib/active_support/notifications.rb:52:in `instrument'
actionpack (3.0.6) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.0.6) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.0.6) lib/abstract_controller/base.rb:119:in `process'
actionpack (3.0.6) lib/abstract_controller/rendering.rb:41:in `process'
actionpack (3.0.6) lib/action_controller/metal.rb:138:in `dispatch'
actionpack (3.0.6) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.0.6) lib/action_controller/metal.rb:178:in `block in action'
actionpack (3.0.6) lib/action_dispatch/routing/route_set.rb:62:in `call'
actionpack (3.0.6) lib/action_dispatch/routing/route_set.rb:62:in `dispatch'
actionpack (3.0.6) lib/action_dispatch/routing/route_set.rb:27:in `call'
rack-mount (0.6.14) lib/rack/mount/route_set.rb:148:in `block in call'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:93:in `block in recognize'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:68:in `optimized_each'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:92:in `recognize'
rack-mount (0.6.14) lib/rack/mount/route_set.rb:139:in `call'
actionpack (3.0.6) lib/action_dispatch/routing/route_set.rb:493:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/head.rb:14:in `call'
rack (1.2.2) lib/rack/methodoverride.rb:24:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/flash.rb:182:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/session/abstract_store.rb:149:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/cookies.rb:302:in `call'
activerecord (3.0.6) lib/active_record/query_cache.rb:32:in `block in call'
activerecord (3.0.6) lib/active_record/connection_adapters/abstract/query_cache.rb:28:in `cache'
activerecord (3.0.6) lib/active_record/query_cache.rb:12:in `cache'
activerecord (3.0.6) lib/active_record/query_cache.rb:31:in `call'
activerecord (3.0.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:354:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/callbacks.rb:46:in `block in call'
activesupport (3.0.6) lib/active_support/callbacks.rb:416:in `_run_call_callbacks'
actionpack (3.0.6) lib/action_dispatch/middleware/callbacks.rb:44:in `call'
rack (1.2.2) lib/rack/sendfile.rb:107:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call'
railties (3.0.6) lib/rails/rack/logger.rb:13:in `call'
rack (1.2.2) lib/rack/runtime.rb:17:in `call'
activesupport (3.0.6) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.2.2) lib/rack/lock.rb:11:in `block in call'
<internal:prelude>:10:in `synchronize'
rack (1.2.2) lib/rack/lock.rb:11:in `call'
actionpack (3.0.6) lib/action_dispatch/middleware/static.rb:30:in `call'
railties (3.0.6) lib/rails/application.rb:168:in `call'
railties (3.0.6) lib/rails/application.rb:77:in `method_missing'
railties (3.0.6) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.2.2) lib/rack/content_length.rb:13:in `call'
rack (1.2.2) lib/rack/handler/webrick.rb:52:in `service'
c:/Ruby192/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'
c:/Ruby192/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run'
c:/Ruby192/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'
Is the ability to edit class properties using the form_for-tag?

Answer 1

jdc answered this, but didn't show the actual implementation you requested. As jdc stated you need to include some ActiveModel modules, which will give your ruby class the features you need.
It looks like you need ActiveModel::Naming and ActiveModel::AttributeMethods.
class Entry
extend ActiveModel::Naming
include ActiveModel::AttributeMethods
end
The first line will give you model_name and the second line allow your model to function with the form helpers. There are other lines you can use: check the blog posted linked in jdc's answer or the Rails API.
More links with detailed information:
http://www.rubyinside.com/rails-3-0s-activemodel-how-to-give-ruby-classes-some-activerecord-magic-2937.html
http://railscasts.com/episodes/219-active-model

Answer 2

This blog entry should get you started:
http://yehudakatz.com/2010/01/10/activemodel-make-any-ruby-object-feel-like-activerecord/
You can include some of the modules ActiveRecord uses to get things like validation and serialization. Then, if you want something like a "save" method that doesn't go to the database, just create one. I did that for a contact model. It's not AR, just a plain old ruby object that pulls in some ActiveModel stuff for validation, provides some required methods, then the save method just fires an e-mail. I think there's even a mixin you can use to take care of that initialization stuff I'm doing to allow mass assignment on creation, but I haven't looked into it that closely. This object looks like an AR object to the front end, so the basic helpers all work.
class Contact
include ActiveModel::Validations
attr_accessor :id, :name, :email, :subject, :body
validates :name, :presence => true
validates :email, :presence => true
validates :subject, :presence => true
validates :body, :presence => true
def initialize(attributes = {})
attributes.each do |key, value|
self.send("#{key}=", value)
end
#attributes = attributes
end
def read_attribute_for_validation(key)
#attributes[key]
end
def to_key
end
def save
if self.valid?
ContactNotifier.website_contact(self).deliver
return true
end
false
end
end

Answer 3

It looks like the error your getting is from the following line in the form_helper.rb:
object_name = options[:as] || ActiveModel::Naming.param_key(object)
If you hardcode in :as => "Entry", you will get a tad farther. Or you could extend the class to respond to the method model_name. Here is the code in ActiveModel::Naming that calls model_name:
def self.model_name_from_record_or_class(record_or_class)
(record_or_class.is_a?(Class) ? record_or_class : convert_to_model(record_or_class).class).model_name
end
I could continue following the calls, but I'd recommend you follow it yourself. Eventually you will find a call that returns a hash of attributes and values that the form builder uses in form_for.
Just look through the rails source, see where your code throws an error, and extend your class to respond to the proper call. Keep doing it and your model will respond fine. You don't need to be an activerecord model to look, walk, and sound like an activerecord model.

Answer 4

I found this RailsCasts Episode#193 to be very helpful with what you're trying to do.

Answer 5

For one thing your entry model file should start like this:
class Entry < ActiveRecord::Base