Rails: Pass parameters with render :action?

Question

I have a form that displays differently depending on the parameter it was called with.

Ex.

testsite.local/users/new?type=client 

So if type was a or b, the form would display different fields.

My problem is when the form is filled out incorrectly, because if the user couldn't be saved corrently, it renders the form with the default error messages, but also without my parameter.

testsite.local/users/new 

How can I call my render action and pass whatever this parameter is set to to it? So that I can still keep my built-in error messages about why the form couldn't be sumbitted properly AND have it be the right form?

Here's my create action:

def create    @user = User.new(params[:user])    roles = params[:user][:assigned_roles]    if @user.save      update_user_roles(@user,roles)      if current_user.is_admin_or_root?        flash[:message] = "User \"#{@user.username}\" created."        redirect_to users_path      else        flash[:message] = "Congrats! You're now registered!"        redirect_to app_path      end    else      render :action => 'new'    end  end 

Answer 1

As elucidated by another user answering my other related question, here's what I was after:

form_for @user, :url => { :action => :create, :type => @type } 

... which preserves the parameter :type through each new render action (assuming I have it defined correctly in my controller).