Tuesday, April 21, 2009

Rails Pagination with AJAX

When I upgraded to Rails 2.0, I quickly found out that pagination was removed from the rails code base.  In order to get it you have to install a plugin.  After searching on the web I found two possible plugins: classic pagination, and will_paginate.  I choose will_paginate because it is more efficient and works directly with the model.

However, the author suggests not to use link_to_remote to implement an "AJAXified" pagination.  Instead he gives some pretty ugly javascript code that does it.  Since I am using a lot of javascript in other areas of my application, I was really hesitant to go down that path and possibly break my javascript functions.  I see his point, in that not everyone uses the prototype library, but I do.  So I came across Redline's blog to change my links to link_to_remote links.  But this violates the other reason the will_paginate's author gives for not using link_to_remote - non-javascript browser support and search engine support.

After looking at the link_to_remote documentation, I found that you can replace the default anchor link location (href="#") with the same url the ajax call goes to.  This allows non-javascript enabled browsers and search engines to follow the links.  I just modified Redline's render to add one extra option to set the href.  This is my renderer module:
# app/helpers/remote_link_renderer.rb

class RemoteLinkRenderer < WillPaginate::LinkRenderer
def prepare(collection, options, template)
@remote = options.delete(:remote) || {}
super
end

protected
def page_link(page, text, attributes = {})
@template.link_to_remote(text, {:url => url_for(page),
:method => :get}.merge(@remote), :href => url_for(page))
end
end

With that, javascript-enabled browsers will use make and use the AJAX calls, and non-javascript-enabled browsers and search engines will use the normal links.  This seems like the cleanest and most DRY way to get pagination with AJAX.

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