Pass additional parameters to a controller

I have this link to create a new page:

<p><%= link_to "Add a page"开发者_开发技巧, :action => "new" %></p>

The code called in the controller is this:

def new
  @page = Page.new
  @visuals = Visual.find(:all)
end

I would like to pass an additional parameter to pre-set a field in the form, something like this:

<p><%= link_to "Add a page", :action => "new/parent_id/2" %></p>

and in the controller

def new
  @page = Page.new
  @page.parent_id = params[:parent_id]
  @visuals = Visual.find(:all)
end

link_to "new", :action => 'new', :parent_id => 1

... will give you:

/controller/new?parent_id=1

If you mess with the routes, you could do:

map.new_page_from_parent "/new_from_parent/:parent_id"

... and use like so:

link_to "new", new_page_from_parent_path(:parent_id => 1)

# gives
/new_from_parent/1

# accessed via
params[:parent_id] => 1

To get a new parameter without changing routes, just pass it in as a query string:

new?parent_id=2

then it will be available to you as params[:parent_id]