title: Complex nested form rails 3 using nested_form gem
body: <p>I have a problem and I don't know how to solve it.</p>
  
  <p>I'm using "nested_form" gem in classic way so I'm able to add "multiple tasks" to a "project" while I'm creating a "project". That's not the problem.</p>
  
  <p>To explain the problem I'm going to use an example. Supose I have two models, "Projects" and "Tasks", where project has many tasks and task belongs to project. But in this case I can create a task without a project (foreign key could be null) and I want to make the association later.</p>
  
  <p>So my idea is, when I create the project I want to associate tasks that already exists, so when i save the project, the foreign key in task should be the id of the project just created</p>
  
  <p>Is that possible??, hope you can help me, thanks</p>