Kaminari

A Scope & Engine based, clean, powerful, customizable and sophisticated paginator for modern web app frameworks and ORMs

Features

Clean

Does not globally pollute Array, Hash, Object or AR::Base.

Easy to Use

Just bundle the gem, then your models are ready to be paginated. No configuration required. Don't have to define anything in your models or helpers.

Simple Scope-based API

Everything is method chainable with less "Hasheritis". You know, that's the modern Rails way. No special collection class or anything for the paginated values, instead using a general AR::Relation instance. So, of course you can chain any other conditions before or after the paginator scope.

Customizable Engine-based I18n-aware Helpers

As the whole pagination helper is basically just a collection of links and non-links, Kaminari renders each of them through its own partial template inside the Engine. So, you can easily modify their behaviour, style or whatever by overriding partial templates.

ORM & Template Engine Agnostic

Kaminari supports multiple ORMs (ActiveRecord, DataMapper, Mongoid, MongoMapper) multiple web frameworks (Rails, Sinatra, Grape), and multiple template engines (ERB, Haml, Slim).

Modern

The pagination helper outputs the HTML5 <nav> tag by default. Plus, the helper supports Rails unobtrusive Ajax.

Supported Versions

• Ruby 2.0.0, 2.1.x, 2.2.x, 2.3.x, 2.4.x, 2.5.x, 2.6.x, 2.7.x, 2.8

• Rails 4.1, 4.2, 5.0, 5.1, 5.2, 6.0, 6.1

• Sinatra 1.4, 2.0

• Haml 3+

• Mongoid 3+

• MongoMapper 0.9+

• DataMapper 1.1.0+

Installation

To install kaminari on the default Rails stack, just put this line in your Gemfile:

gem 'kaminari'

Then bundle:

% bundle

If you're building non-Rails of non-ActiveRecord app and want the pagination feature on it, please take a look at Other Framework/Library Support section.

Query Basics

The page Scope

To fetch the 7th page of users (default per_page is 25)

User.page(7)

Note: pagination starts at page 1, not at page 0 (page(0) will return the same results as page(1)).

You can get page numbers or page conditions by using below methods.

User.count                     #=> 1000
User.page(1).limit_value       #=> 20
User.page(1).total_pages       #=> 50
User.page(1).current_page      #=> 1
User.page(1).next_page         #=> 2
User.page(2).prev_page         #=> 1
User.page(1).first_page?       #=> true
User.page(50).last_page?       #=> true
User.page(100).out_of_range?   #=> true

The per Scope

To show a lot more users per each page (change the per_page value)

User.page(7).per(50)

Note that the per scope is not directly defined on the models but is just a method defined on the page scope. This is absolutely reasonable because you will never actually use per_page without specifying the page number.

Keep in mind that per internally utilizes limit and so it will override any limit that was set previously. And if you want to get the size for all request records you can use total_count method:

User.count                     #=> 1000
a = User.limit(5); a.count     #=> 5
a.page(1).per(20).size         #=> 20
a.page(1).per(20).total_count  #=> 1000

The padding Scope

Occasionally you need to pad a number of records that is not a multiple of the page size.

User.page(7).per(50).padding(3)

Note that the padding scope also is not directly defined on the models.

Unscoping

If for some reason you need to unscope page and per methods you can call except(:limit, :offset)

users = User.page(7).per(50)
unpaged_users = users.except(:limit, :offset) # unpaged_users will not use the kaminari scopes

Configuring Kaminari

General Configuration Options

You can configure the following default values by overriding these values using Kaminari.configure method.

default_per_page      # 25 by default
max_per_page          # nil by default
max_pages             # nil by default
window                # 4 by default
outer_window          # 0 by default
left                  # 0 by default
right                 # 0 by default
page_method_name      # :page by default
param_name            # :page by default
params_on_first_page  # false by default

There's a handy generator that generates the default configuration file into config/initializers directory. Run the following generator command, then edit the generated file.

% rails g kaminari:config

Changing page_method_name

You can change the method name page to bonzo or plant or whatever you like, in order to play nice with existing page method or association or scope or any other plugin that defines page method on your models.

Configuring Default per_page Value for Each Model by paginates_per

You can specify default per_page value per each model using the following declarative DSL.

class User < ActiveRecord::Base
  paginates_per 50
end

Configuring Max per_page Value for Each Model by max_paginates_per

You can specify max per_page value per each model using the following declarative DSL. If the variable that specified via per scope is more than this variable, max_paginates_per is used instead of it. Default value is nil, which means you are not imposing any max per_page value.

class User < ActiveRecord::Base
  max_paginates_per 100
end

Controllers

The Page Parameter Is in params[:page]

Typically, your controller code will look like this:

@users = User.order(:name).page params[:page]

Views

The Same Old Helper Method

Just call the paginate helper:

<%= paginate @users %>

This will render several ?page=N pagination links surrounded by an HTML5 <nav> tag.

Helpers

The paginate Helper Method

<%= paginate @users %>

This would output several pagination links such as « First ‹ Prev ... 2 3 4 5 6 7 8 9 10 ... Next › Last »

Specifying the "inner window" Size (4 by default)

<%= paginate @users, window: 2 %>

This would output something like ... 5 6 7 8 9 ... when 7 is the current page.

Specifying the "outer window" Size (0 by default)

<%= paginate @users, outer_window: 3 %>

This would output something like 1 2 3 ...(snip)... 18 19 20 while having 20 pages in total.

Outer Window Can Be Separately Specified by left, right (0 by default)

<%= paginate @users, left: 1, right: 3 %>

This would output something like 1 ...(snip)... 18 19 20 while having 20 pages in total.

Changing the Parameter Name (:param_name) for the Links

<%= paginate @users, param_name: :pagina %>

This would modify the query parameter name on each links.

Extra Parameters (:params) for the Links

<%= paginate @users, params: {controller: 'foo', action: 'bar'} %>

This would modify each link's url_option. :controller and :action might be the keys in common.

Ajax Links (crazy simple, but works perfectly!)

<%= paginate @users, remote: true %>

This would add data-remote="true" to all the links inside.

Specifying an Alternative Views Directory (default is kaminari/)

<%= paginate @users, views_prefix: 'templates' %>

This would search for partials in app/views/templates/kaminari. This option makes it easier to do things like A/B testing pagination templates/themes, using new/old templates at the same time as well as better integration with other gems such as cells.

The link_to_next_page and link_to_previous_page (aliased to link_to_prev_page) Helper Methods

<%= link_to_next_page @items, 'Next Page' %>

This simply renders a link to the next page. This would be helpful for creating a Twitter-like pagination feature.

The page_entries_info Helper Method

<%= page_entries_info @posts %>

This renders a helpful message with numbers of displayed vs. total entries.

By default, the message will use the humanized class name of objects in collection: for instance, "project types" for ProjectType models. The namespace will be cut out and only the last name will be used. Override this with the :entry_name parameter:

<%= page_entries_info @posts, entry_name: 'item' %>
#=> Displaying items 6 - 10 of 26 in total

The rel_next_prev_link_tags Helper Method

<%= rel_next_prev_link_tags @users %>

This renders the rel next and prev link tags for the head.

The path_to_next_page Helper Method

<%= path_to_next_page @users %>

This returns the server relative path to the next page.

The path_to_prev_page Helper Method

<%= path_to_prev_page @users %>

This returns the server relative path to the previous page.

I18n and Labels

The default labels for 'first', 'last', 'previous', '...' and 'next' are stored in the I18n yaml inside the engine, and rendered through I18n API. You can switch the label value per I18n.locale for your internationalized application. Keys and the default values are the following. You can override them by adding to a YAML file in your Rails.root/config/locales directory.

en:
  views:
    pagination:
      first: "« First"
      last: "Last »"
      previous: "‹ Prev"
      next: "Next ›"
      truncate: "…"
  helpers:
    page_entries_info:
      one_page:
        display_entries:
          zero: "No %{entry_name} found"
          one: "Displaying <b>1</b> %{entry_name}"
          other: "Displaying <b>all %{count}</b> %{entry_name}"
      more_pages:
        display_entries: "Displaying %{entry_name} <b>%{first}&nbsp;-&nbsp;%{last}</b> of <b>%{total}</b> in total"

If you use non-English localization see i18n rules for changing one_page:display_entries block.

Customizing the Pagination Helper

Kaminari includes a handy template generator.

To Edit Your Paginator

Run the generator first,

% rails g kaminari:views default

then edit the partials in your app's app/views/kaminari/ directory.

For Haml/Slim Users

You can use the html2haml gem or the html2slim gem to convert erb templates. The kaminari gem will automatically pick up haml/slim templates if you place them in app/views/kaminari/.

Multiple Templates

In case you need different templates for your paginator (for example public and admin), you can pass --views-prefix directory like this:

% rails g kaminari:views default --views-prefix admin

that will generate partials in app/views/admin/kaminari/ directory.

Themes

The generator has the ability to fetch several sample template themes from the external repository (https://github.com/amatsuda/kaminari_themes) in addition to the bundled "default" one, which will help you creating a nice looking paginator.

% rails g kaminari:views THEME

To see the full list of available themes, take a look at the themes repository, or just hit the generator without specifying THEME argument.

% rails g kaminari:views

Multiple Themes

To utilize multiple themes from within a single application, create a directory within the app/views/kaminari/ and move your custom template files into that directory.

% rails g kaminari:views default (skip if you have existing kaminari views)
% cd app/views/kaminari
% mkdir my_custom_theme
% cp _*.html.* my_custom_theme/

Next, reference that directory when calling the paginate method:

<%= paginate @users, theme: 'my_custom_theme' %>

Customize away!

Note: if the theme isn't present or none is specified, kaminari will default back to the views included within the gem.

Paginating Without Issuing SELECT COUNT Query

Generally the paginator needs to know the total number of records to display the links, but sometimes we don't need the total number of records and just need the "previous page" and "next page" links. For such use case, Kaminari provides without_count mode that creates a paginatable collection without counting the number of all records. This may be helpful when you're dealing with a very large dataset because counting on a big table tends to become slow on RDBMS.

Just add .without_count to your paginated object:

User.page(3).without_count

In your view file, you can only use simple helpers like the following instead of the full-featured paginate helper:

<%= link_to_prev_page @users, 'Previous Page' %>
<%= link_to_next_page @users, 'Next Page' %>

Paginating a Generic Array object

Kaminari provides an Array wrapper class that adapts a generic Array object to the paginate view helper. However, the paginate helper doesn't automatically handle your Array object (this is intentional and by design). Kaminari::paginate_array method converts your Array object into a paginatable Array that accepts page method.

@paginatable_array = Kaminari.paginate_array(my_array_object).page(params[:page]).per(10)

You can specify the total_count value through options Hash. This would be helpful when handling an Array-ish object that has a different count value from actual count such as RSolr search result or when you need to generate a custom pagination. For example:

@paginatable_array = Kaminari.paginate_array([], total_count: 145).page(params[:page]).per(10)

or, in the case of using an external API to source the page of data:

page_size = 10
one_page = get_page_of_data params[:page], page_size
@paginatable_array = Kaminari.paginate_array(one_page.data, total_count: one_page.total_count).page(params[:page]).per(page_size)

Creating Friendly URLs and Caching

Because of the page parameter and Rails routing, you can easily generate SEO and user-friendly URLs. For any resource you'd like to paginate, just add the following to your routes.rb:

resources :my_resources do
  get 'page/:page', action: :index, on: :collection
end

If you are using Rails 4 or later, you can simplify route definitions by using concern:

concern :paginatable do
  get '(page/:page)', action: :index, on: :collection, as: ''
end

resources :my_resources, concerns: :paginatable

This will create URLs like /my_resources/page/33 instead of /my_resources?page=33. This is now a friendly URL, but it also has other added benefits...

Because the page parameter is now a URL segment, we can leverage on Rails page caching!

NOTE: In this example, I've pointed the route to my :index action. You may have defined a custom pagination action in your controller - you should point action: :your_custom_action instead.

Other Framework/Library Support

The kaminari gem

Technically, the kaminari gem consists of 3 individual components:

kaminari-core: the core pagination logic
kaminari-activerecord: Active Record adapter
kaminari-actionview: Action View adapter

So, bundling gem 'kaminari' is equivalent to the following 2 lines (kaminari-core is referenced from the adapters):

gem 'kaminari-activerecord'
gem 'kaminari-actionview'

For Other ORM Users

If you want to use other supported ORMs instead of ActiveRecord, for example Mongoid, bundle its adapter instead of kaminari-activerecord.

gem 'kaminari-mongoid'
gem 'kaminari-actionview'

Kaminari currently provides adapters for the following ORMs:

• Active Record: https://github.com/kaminari/kaminari/tree/master/kaminari-activerecord (included in this repo)
• Mongoid: https://github.com/kaminari/kaminari-mongoid
• MongoMapper: https://github.com/kaminari/kaminari-mongo_mapper
• DataMapper: https://github.com/kaminari/kaminari-data_mapper (would not work on kaminari 1.0.x)

For Other Web Framework Users

If you want to use other web frameworks instead of Rails + Action View, for example Sinatra, bundle its adapter instead of kaminari-actionview.

gem 'kaminari-activerecord'
gem 'kaminari-sinatra'

Kaminari currently provides adapters for the following web frameworks:

• Action View: https://github.com/kaminari/kaminari/tree/master/kaminari-actionview (included in this repo)
• Sinatra: https://github.com/kaminari/kaminari-sinatra
• Grape: https://github.com/kaminari/kaminari-grape

For More Information

Check out Kaminari recipes on the GitHub Wiki for more advanced tips and techniques. https://github.com/kaminari/kaminari/wiki/Kaminari-recipes

Questions, Feedback

Feel free to message me on Github (amatsuda) or Twitter (@a_matsuda) ☇☇☇ :)

Contributing to Kaminari

Fork, fix, then send a pull request.

To run the test suite locally against all supported frameworks:

% bundle install
% rake test:all

To target the test suite against one framework:

% rake test:active_record_50

You can find a list of supported test tasks by running rake -T. You may also find it useful to run a specific test for a specific framework. To do so, you'll have to first make sure you have bundled everything for that configuration, then you can run the specific test:

% BUNDLE_GEMFILE='gemfiles/active_record_50.gemfile' bundle install
% BUNDLE_GEMFILE='gemfiles/active_record_50.gemfile' TEST=kaminari-core/test/requests/navigation_test.rb bundle exec rake test

Copyright

Copyright (c) 2011- Akira Matsuda. See MIT-LICENSE for further details.