Add querystring parameters to link_to

Question

I'm having difficultly adding querystring parameters to link_to UrlHelper. I have an Index view, for example, that has UI elements for sorting, filtering, and pagination (via will_paginate). The will_paginate plugin manages the intra-page persistence of querystring parameters correctly.

Is there an automatic mechanism to add the querystring parameters to a give named route, or do I need to do so manually? A great deal of research on this seemingly simple construct has left me clueless.

Edit

Some of the challenges:

1. If I have two querystring parameters, bucket & sorting, how do set a specific value to one of these in a link_to, while preserving the current value of the other? For example:

   <%= link_to "0", profiles_path(:bucket => '0', :sorting=>?? ) %>
   

2. If I have multiple querystring parameters, bucket & sorting & page_size, and I want to set the value to one of these, is there a way to 'automatically' include the names and values of the remaining parameters? For example:

   <%= link_to "0", profiles_path(:bucket => '0', [include sorting and page_size name/values here] ) %>
   

3. The will_paginate plugin manages its page variable and other querystring variables automatically. There doesn't seem to be an automatic UI element for managing page size. While I've seen code to create a select list of page sizes, I would rather have A elements for this (like SO). Part of this challenge is related to #2, part is related to hiding/showing this UI element based on the existence/non-existence of records. Said another way, I only want to include page-size links if there are records to page. Moreover, I prefer to automatically include the other QS variables (i.e. page, bucket, sorting), rather than having to include them by name in the link_to.

Answer 1

The API docs on link_to show some examples of adding querystrings to both named and oldstyle routes. Is this what you want?

link_to can also produce links with anchors or query strings:

link_to "Comment wall", profile_path(@profile, :anchor => "wall")
#=> <a href="/profiles/1#wall">Comment wall</a>

link_to "Ruby on Rails search", :controller => "searches", :query => "ruby on rails"
#=> <a href="/searches?query=ruby+on+rails">Ruby on Rails search</a>

link_to "Nonsense search", searches_path(:foo => "bar", :baz => "quux")
#=> <a href="/searches?foo=bar&amp;baz=quux">Nonsense search</a>