[ruby-on-rails] Add querystring parameters to link_to

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.

If you want to keep existing params and not expose yourself to XSS attacks, be sure to clean the params hash, leaving only the params that your app can be sending:

# inline
<%= link_to 'Link', params.slice(:sort).merge(per_page: 20) %>

If you use it in multiple places, clean the params in the controller:

# your_controller.rb
@params = params.slice(:sort, :per_page)

# view
<%= link_to 'Link', @params.merge(per_page: 20) %>

In case you want to pass in a block, say, for a glyphicon button, as in the following:

<%= link_to my_url, class: "stuff" do %>
  <i class="glyphicon glyphicon-inbox></i> Nice glyph-button
<% end %>

Then passing querystrings params could be accomplished through:

<%= link_to url_for(params.merge(my_params: "value")), class: "stuff" do %>
  <i class="glyphicon glyphicon-inbox></i> Nice glyph-button
<% end %>

If you want the quick and dirty way and don't worry about XSS attack, use params.merge to keep previous parameters. e.g.

<%= link_to 'Link', params.merge({:per_page => 20}) %>

see: https://stackoverflow.com/a/4174493/445908

Otherwise , check this answer: params.merge and cross site scripting