Rails form_tag form writing - with non-active record model

问题

I'm somewhat of a Rails newbie. I'm writing a couchrest-rails app, so am not using activerecord for this model. I just figured out that that means that

form_for(@model) 

won't work. I'm trying to work out how to use form_tag -- but most of the examples don't involve new & create actions.

This is wrong:

<h1>New article</h1>

<% form_tag new_article_url(@article), :method => :post do |f| %>
  <%= f.error_messages %>

  <p>
    <%= f.label :title %><br />
    <%= f.text_field :title %>
  </p>
  <p>
    <%= f.submit 'Create' %>
  </p>
<% end %>

<%= link_to 'Back', articles_path %>

Because when I run my Cucumber scenario, I get this:

Scenario: Create Valid Article                            # features/article.feature:16
  Given I have no articles                                # features/step_definitions /article_steps.rb:8
  And I am on the list of articles                        # features/step_definitions/webrat_steps.rb:6
/home/deploy/www/www.trackingplace.com/app/ccc/app/views/articles/new.html.erb:3: warning: multiple values for a block parameter (0 for 1)
from /usr/local/lib/ruby/gems/1.8/gems/actionpack-2.3.3/lib/action_view/helpers/capture_helper.rb:36
When I follow "New Article"                             # features/step_definitions/webrat_steps.rb:18
  You have a nil object when you didn't expect it!
  The error occurred while evaluating nil.error_messages (ActionView::TemplateError)
  features/article.feature:19:in `When I follow "New Article"'

But I don't understand the error, or how to fix it.

回答1:

The form_tag method does not use a form builder, so you can't use the "f" variable in the form block. Instead of f.error_messages you have to use error_messages_for, etc.

<% form_tag new_article_url(@article), :method => :post do %>
  <%= error_messages_for :article %>

  <p>
    <%= label :article, :title %><br />
    <%= text_field :article, :title %>
  </p>
  <p>
    <%= submit_tag 'Create' %>
  </p>
<% end %>

That said, you can use form_for with non ActiveRecord objects, they just need to respond to certain methods. Ensure that these methods are implemented in the Article model.

• id
• new_record?
• to_param
• errors

That's just a guess as to what is needed, there may be others. If these are implemented and behave like ActiveRecord does you should be able to use form_for.

来源：https://stackoverflow.com/questions/1273263/rails-form-tag-form-writing-with-non-active-record-model