title: rails: fields_for and collection
body: <p>i would like to use an additional collection for a fields_for. this collection should hold all the possibilities to be used in fields_for.</p>
  
  <p>Lets say I have a person with tasks that will happen regularly each week on the same day. In the person form, i should have an entry for each day, even if there are not yet any saved tasks. I tried:</p>
  
  <pre><code>&lt;% form_for(@person) do |f| %&gt;
  ...
  
    &lt;% f.fields_for :tasks, @weekdays do |task_fields| %&gt; 
      &lt;%= weekday.name %&gt;: 
      &lt;%= project_fields.text_field :name %&gt;
    &lt;% end %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>now there should be for each weekday a text field to enter the name of the task of that day. for example weekday.name = "monday" and task.name = "drinking coffee", task.weekday_id = 1</p>