How do I pass values that aren't part of the Model through a form in Rails?

I have a form used for creating a new record of the model Message.

However, the route to create this has been customized to look like:

  match 'messages/:sender_id/to/:receiver_id' => "messages#new", :as => :send_message

I want from the new action to then pass the values for :sender_id and :receiver_id so I can I assign it to a related model, called UserHasMessages.

This model needs to be created whenever a new record for Message is created.

But I can't use hidden fields because :sender_id is NOT an attribute of Message. it is an attribute of UserHasMessages.

Thanks.

controller/messages_controller.rb

 def create
 15     @message = Message.new(params[:message])
 16     if @message.save
 17       @user_has_message = UserHasMessages.new
 18       @user_has_message.user_id = params[:sender_id]
 19       @user_has_message.message_id = @message.id
 20       @user_has_message.开发者_如何学Gois_sender = 1
 21       @user_has_message.save
 22       
 23       @user_has_message = UserHasMessages.new
 24       @user_has_message.user_id = params[:receiver_id]
 25       @user_has_message.message_id = @message.id
 26       @user_has_message.is_sender = 0
 27       @user_has_message.save

view/messages/_form.

<%= form_for @message do |f| %>
  2   <%= f.error_messages %>
  3   <p>
  4     <%= f.label :subject %><br />
  5     <%= f.text_field :subject %>
  6   </p>
  7   <p>
  8     <%= f.label :body %><br />
  9     <%= f.text_area :body %>
 10   </p>
 11   <p>
 12     <%= f.label :contact_id %><br />
 13     <%= f.text_field :contact_id %>
 14   </p>
 15   <p>
 16     <%= f.label :company_id %><br />
 17     <%= f.text_field :company_id %>
 18   </p>
 19   <p> 
 20       
 21     <%= hidden_field_tag :sender_id, :value => params[:sender_id] %>
 22     <%= hidden_field_tag :receiver_id, :value => params[:receiver_id] %>
 23   </p>
 24       
 25   <p><%= f.submit %></p>
 26 <% end %>

message_controller/new

10   def new
 11     @message = Message.new
 12   end

In the form_for, it is possible to pass stand alone values not related to the model object like this

form_for :message do |f|
  f.text_field ..
  ...
  hidden_field_tag :sender_id, params[:sender_id]
  hidden_field_tag :receiver_id, params[:receiver_id]
end

These can be accessed in create method as params[:sender_id] and params[:receiver_id]

i'm not sure i understand your question... Let's try according to what i understand so far :)

i believe whatever parameter you put in a form field will be accessible in the params hash of your controller. For instance, if you put a form field named 'test_field', then in your controller you'll be able to read it's value via params[:test_field].

In your controller, i recommend you put a line like this while testing: puts params.inspect

Hope that helps! Pierre.