Action Pack pagination for Active Record collections

DEPRECATION WARNING: Pagination will be moved to a plugin in Rails 2.0. Install the classic_pagination plugin for forward compatibility:

script/plugin install svn://errtheblog.com/svn/plugins/classic_pagination

The Pagination module aids in the process of paging large collections of Active Record objects. It offers macro-style automatic fetching of your model for multiple views, or explicit fetching for single actions. And if the magic isn’t flexible enough for your needs, you can create your own paginators with a minimal amount of code.

The Pagination module can handle as much or as little as you wish. In the controller, have it automatically query your model for pagination; or, if you prefer, create Paginator objects yourself.

Pagination is included automatically for all controllers.

For help rendering pagination links, see ActionView::Helpers::PaginationHelper.

Automatic pagination for every action in a controller

class PersonController < ApplicationController   
  model :person

  paginate :people, :order => 'last_name, first_name',
           :per_page => 20

  # ...
end

Each action in this controller now has access to a @people instance variable, which is an ordered collection of model objects for the current page (at most 20, sorted by last name and first name), and a @person_pages Paginator instance. The current page is determined by the params[:page] variable.

Pagination for a single action

def list
  @person_pages, @people =
    paginate :people, :order => 'last_name, first_name'
end

Like the previous example, but explicitly creates @person_pages and @people for a single action, and uses the default of 10 items per page.

Custom/“classic” pagination 

def list
  @person_pages = Paginator.new self, Person.count, 10, params[:page]
  @people = Person.find :all, :order => 'last_name, first_name', 
                        :limit  =>  @person_pages.items_per_page,
                        :offset =>  @person_pages.current.offset
end

Explicitly creates the paginator from the previous example and uses Paginator#to_sql to retrieve @people from the model.

Namespace
Methods
C
F
P
Constants
OPTIONS = Hash.new
 

A hash holding options for controllers using macro-style pagination
DEFAULT_OPTIONS = { :class_name => nil, :singular_name => nil, :per_page => 10, :conditions => nil, :order_by => nil, :order => nil, :join => nil, :joins => nil, :count => nil, :include => nil, :select => nil, :parameter => 'page' }
 

The default options for pagination
Instance Public methods
paginate(collection_id, options={})

Returns a paginator and a collection of Active Record model instances for the paginator’s current page. This is designed to be used in a single action; to automatically paginate multiple actions, consider ActionController::Pagination::ClassMethods#paginate.

options are:

:singular_name

the singular name to use, if it can’t be inferred by singularizing the collection name

:class_name

the class name to use, if it can’t be inferred by camelizing the singular name

:per_page

the maximum number of items to include in a single page. Defaults to 10

:conditions

optional conditions passed to Model.find(:all, *params) and Model.count

:order

optional order parameter passed to Model.find(:all, *params)

:order_by

(deprecated, used :order) optional order parameter passed to Model.find(:all, *params)

:joins

optional joins parameter passed to Model.find(:all, *params) and Model.count

:join

(deprecated, used :joins or :include) optional join parameter passed to Model.find(:all, *params) and Model.count

:include

optional eager loading parameter passed to Model.find(:all, *params) and Model.count

:select

:select parameter passed to Model.find(:all, *params)

:count

parameter passed as :select option to Model.count(*params)

Source: show 

# File rails/actionpack/lib/action_controller/pagination.rb, line 130
def paginate(collection_id, options={})
  Pagination.validate_options!(collection_id, options, true)
  paginator_and_collection_for(collection_id, options)
end
Instance Protected methods
count_collection_for_pagination(model, options)

Returns the total number of items in the collection to be paginated for the model and given conditions. Override this method to implement a custom counter.

Source: show 

# File rails/actionpack/lib/action_controller/pagination.rb, line 178
def count_collection_for_pagination(model, options)
  model.count(:conditions => options[:conditions],
              :joins => options[:join] || options[:joins],
              :include => options[:include],
              :select => options[:count])
end
find_collection_for_pagination(model, options, paginator)

Returns a collection of items for the given model and +options+, ordered by +options+, for the current page in the given paginator. Override this method to implement a custom finder.

Source: show 

# File rails/actionpack/lib/action_controller/pagination.rb, line 188
def find_collection_for_pagination(model, options, paginator)
  model.find(:all, :conditions => options[:conditions],
             :order => options[:order_by] || options[:order],
             :joins => options[:join] || options[:joins], :include => options[:include],
             :select => options[:select], :limit => options[:per_page],
             :offset => paginator.current.offset)
end