Passing instance variable from one form to the a different controller's action in Rails

Question

Hi,

Simple question - I have a form where I create an instance of an object. After I create that object (aka submit the form), I want to redirect to a new form that is associated with a different controller's action and carry that instance variable to populate some of that form's fields.

I know I typically have 2 options, store that instance variable in the session or pass it via params. I can't use sessions (for a variety of reasons I won't bore you with). The params option I am confused on.

I should know this. :( How would you go about doing this? Any examples greatly appreciated!!

Betsy

Answer 1

You'll have two methods on your controller. One for each form (rendered by the associated template). The first form should post to the second action. The second action can then transfer the request parameters into instance variables, to be available within the second template.

class FooController
  def bar
   # setup instance variables and render first form
  end

  def baz
    @bar_values = params[:bar]
    # setup other instance variables and render second form
  end
end

UPDATE0 Do it across two controllers using session.

class FooController
  def new_baz
    # setup instance variables and render the first form
  end

  def create_baz
    # respond to posting of form data
    session[:current_baz_values] = params
    redirect_to :action => "baq", :controller => "bar"
  end
end

class BarController
  def baq
    @baz_values = session[:current_baz_values]
    # setup other instance variables and render the second form
  end
end

Answer 2

Could you somehow just do a find of the newly created record in the other controller, and then use that to populate the info you need?

Also, unless you are using AJAX you usually don't want to have modification actions on the show page for a record. Those belong on the edit or update page. If you always want people to be able to edit a record on the same page I would either use some AJAX on the show page, or just always return the edit/update page instead...

Answer 3

If you do not want to use sessions, you could use the flash variable to store your parameter. Something like, flash[:my_params] = params, and then reading it back in the next request with params = flash[:my_params]. The good thing about flash, is that persists for only the next request, and auto-clears after that.

If you are looking for passing values from the client side when using Ajax, then probably setting a hidden field with the parameters is going to pass them on to the next request.