Cursed

Cursed is a gem that implements the cursoring pattern in Postgres with the ActiveRecord and Sequel gems. The cursoring pattern is an alternative to traditional pagination which is superior in that it is stable for collections that are constantly changing.

Instead of providing a parameter page we instead provide any of three parameters before, after and limit (you may customize these as you wish). By choosing to 'paginate' by providing the maximum ID you know about you can be assured that the same record will not appear twice if records behind it have changed it's position.

Installation

Add this line to your application's Gemfile:

gem 'cursed'

And then execute:

$ bundle

Or install it yourself as:

$ gem install cursed

Usage

In your controller code call your collection in this manner.

Cursed::Collection.new(
  relation: MyModel.unscoped,
  cursor: Cursed::Cursor.new(
    after: params[:after],
    before: params[:before],
    limit: params[:limit],
    maximum: 20
  )
)

The Collection is enumerable so you can use it as you would us any array

<% @collection.each do |record| %>
  <%= record.name %>
<% end %>

To generate your next link and previous link merge in the values of #next_page_params and #prev_page_params into your URL generator. #next_page? and #prev_page? can be used to determine if there are next or previous pages of records currently.

  <% if collection.prev_page? %>
    <%= link_to 'Previous Page', widgets_path(collection.prev_page_params) %>
  <% end %>
  <% if collection.next_page? %>
    <%= link_to 'Next Page', widgets_path(collection.next_page_params) %>
  <% end %>

Development

After checking out the repo, run bin/setup to install dependencies. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/influitive/cursed.

License

This gem is licensed under the MIT license.