406 lines
15 KiB
Ruby
406 lines
15 KiB
Ruby
module ActionController
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# === Action Pack pagination for Active Record collections
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#
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# The Pagination module aids in the process of paging large collections of
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# Active Record objects. It offers macro-style automatic fetching of your
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# model for multiple views, or explicit fetching for single actions. And if
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# the magic isn't flexible enough for your needs, you can create your own
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# paginators with a minimal amount of code.
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#
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# The Pagination module can handle as much or as little as you wish. In the
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# controller, have it automatically query your model for pagination; or,
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# if you prefer, create Paginator objects yourself.
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#
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# Pagination is included automatically for all controllers.
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#
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# For help rendering pagination links, see
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# ActionView::Helpers::PaginationHelper.
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#
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# ==== Automatic pagination for every action in a controller
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#
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# class PersonController < ApplicationController
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# model :person
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#
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# paginate :people, :order => 'last_name, first_name',
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# :per_page => 20
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#
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# # ...
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# end
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#
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# Each action in this controller now has access to a <tt>@people</tt>
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# instance variable, which is an ordered collection of model objects for the
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# current page (at most 20, sorted by last name and first name), and a
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# <tt>@person_pages</tt> Paginator instance. The current page is determined
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# by the <tt>params[:page]</tt> variable.
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#
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# ==== Pagination for a single action
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#
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# def list
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# @person_pages, @people =
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# paginate :people, :order => 'last_name, first_name'
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# end
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#
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# Like the previous example, but explicitly creates <tt>@person_pages</tt>
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# and <tt>@people</tt> for a single action, and uses the default of 10 items
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# per page.
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#
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# ==== Custom/"classic" pagination
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#
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# def list
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# @person_pages = Paginator.new self, Person.count, 10, params[:page]
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# @people = Person.find :all, :order => 'last_name, first_name',
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# :limit => @person_pages.items_per_page,
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# :offset => @person_pages.current.offset
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# end
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#
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# Explicitly creates the paginator from the previous example and uses
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# Paginator#to_sql to retrieve <tt>@people</tt> from the model.
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#
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module Pagination
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unless const_defined?(:OPTIONS)
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# A hash holding options for controllers using macro-style pagination
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OPTIONS = Hash.new
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# The default options for pagination
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DEFAULT_OPTIONS = {
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:class_name => nil,
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:singular_name => nil,
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:per_page => 10,
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:conditions => nil,
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:order_by => nil,
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:order => nil,
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:join => nil,
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:joins => nil,
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:count => nil,
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:include => nil,
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:select => nil,
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:group => nil,
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:parameter => 'page'
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}
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else
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DEFAULT_OPTIONS[:group] = nil
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end
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def self.included(base) #:nodoc:
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super
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base.extend(ClassMethods)
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end
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def self.validate_options!(collection_id, options, in_action) #:nodoc:
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options.merge!(DEFAULT_OPTIONS) {|key, old, new| old}
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valid_options = DEFAULT_OPTIONS.keys
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valid_options << :actions unless in_action
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unknown_option_keys = options.keys - valid_options
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raise ActionController::ActionControllerError,
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"Unknown options: #{unknown_option_keys.join(', ')}" unless
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unknown_option_keys.empty?
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options[:singular_name] ||= Inflector.singularize(collection_id.to_s)
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options[:class_name] ||= Inflector.camelize(options[:singular_name])
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end
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# Returns a paginator and a collection of Active Record model instances
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# for the paginator's current page. This is designed to be used in a
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# single action; to automatically paginate multiple actions, consider
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# ClassMethods#paginate.
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#
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# +options+ are:
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# <tt>:singular_name</tt>:: the singular name to use, if it can't be inferred by singularizing the collection name
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# <tt>:class_name</tt>:: the class name to use, if it can't be inferred by
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# camelizing the singular name
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# <tt>:per_page</tt>:: the maximum number of items to include in a
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# single page. Defaults to 10
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# <tt>:conditions</tt>:: optional conditions passed to Model.find(:all, *params) and
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# Model.count
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# <tt>:order</tt>:: optional order parameter passed to Model.find(:all, *params)
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# <tt>:order_by</tt>:: (deprecated, used :order) optional order parameter passed to Model.find(:all, *params)
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# <tt>:joins</tt>:: optional joins parameter passed to Model.find(:all, *params)
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# and Model.count
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# <tt>:join</tt>:: (deprecated, used :joins or :include) optional join parameter passed to Model.find(:all, *params)
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# and Model.count
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# <tt>:include</tt>:: optional eager loading parameter passed to Model.find(:all, *params)
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# and Model.count
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# <tt>:select</tt>:: :select parameter passed to Model.find(:all, *params)
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#
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# <tt>:count</tt>:: parameter passed as :select option to Model.count(*params)
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#
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# <tt>:group</tt>:: :group parameter passed to Model.find(:all, *params). It forces the use of DISTINCT instead of plain COUNT to come up with the total number of records
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#
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def paginate(collection_id, options={})
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Pagination.validate_options!(collection_id, options, true)
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paginator_and_collection_for(collection_id, options)
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end
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# These methods become class methods on any controller
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module ClassMethods
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# Creates a +before_filter+ which automatically paginates an Active
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# Record model for all actions in a controller (or certain actions if
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# specified with the <tt>:actions</tt> option).
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#
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# +options+ are the same as PaginationHelper#paginate, with the addition
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# of:
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# <tt>:actions</tt>:: an array of actions for which the pagination is
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# active. Defaults to +nil+ (i.e., every action)
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def paginate(collection_id, options={})
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Pagination.validate_options!(collection_id, options, false)
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module_eval do
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before_filter :create_paginators_and_retrieve_collections
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OPTIONS[self] ||= Hash.new
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OPTIONS[self][collection_id] = options
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end
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end
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end
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def create_paginators_and_retrieve_collections #:nodoc:
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Pagination::OPTIONS[self.class].each do |collection_id, options|
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next unless options[:actions].include? action_name if
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options[:actions]
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paginator, collection =
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paginator_and_collection_for(collection_id, options)
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paginator_name = "@#{options[:singular_name]}_pages"
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self.instance_variable_set(paginator_name, paginator)
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collection_name = "@#{collection_id.to_s}"
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self.instance_variable_set(collection_name, collection)
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end
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end
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# Returns the total number of items in the collection to be paginated for
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# the +model+ and given +conditions+. Override this method to implement a
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# custom counter.
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def count_collection_for_pagination(model, options)
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model.count(:conditions => options[:conditions],
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:joins => options[:join] || options[:joins],
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:include => options[:include],
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:select => (options[:group] ? "DISTINCT #{options[:group]}" : options[:count]))
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end
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# Returns a collection of items for the given +model+ and +options[conditions]+,
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# ordered by +options[order]+, for the current page in the given +paginator+.
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# Override this method to implement a custom finder.
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def find_collection_for_pagination(model, options, paginator)
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model.find(:all, :conditions => options[:conditions],
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:order => options[:order_by] || options[:order],
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:joins => options[:join] || options[:joins], :include => options[:include],
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:select => options[:select], :limit => options[:per_page],
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:group => options[:group], :offset => paginator.current.offset)
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end
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protected :create_paginators_and_retrieve_collections,
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:count_collection_for_pagination,
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:find_collection_for_pagination
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def paginator_and_collection_for(collection_id, options) #:nodoc:
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klass = options[:class_name].constantize
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page = params[options[:parameter]]
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count = count_collection_for_pagination(klass, options)
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paginator = Paginator.new(self, count, options[:per_page], page)
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collection = find_collection_for_pagination(klass, options, paginator)
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return paginator, collection
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end
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private :paginator_and_collection_for
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# A class representing a paginator for an Active Record collection.
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class Paginator
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include Enumerable
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# Creates a new Paginator on the given +controller+ for a set of items
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# of size +item_count+ and having +items_per_page+ items per page.
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# Raises ArgumentError if items_per_page is out of bounds (i.e., less
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# than or equal to zero). The page CGI parameter for links defaults to
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# "page" and can be overridden with +page_parameter+.
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def initialize(controller, item_count, items_per_page, current_page=1)
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raise ArgumentError, 'must have at least one item per page' if
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items_per_page <= 0
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@controller = controller
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@item_count = item_count || 0
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@items_per_page = items_per_page
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@pages = {}
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self.current_page = current_page
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end
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attr_reader :controller, :item_count, :items_per_page
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# Sets the current page number of this paginator. If +page+ is a Page
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# object, its +number+ attribute is used as the value; if the page does
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# not belong to this Paginator, an ArgumentError is raised.
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def current_page=(page)
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if page.is_a? Page
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raise ArgumentError, 'Page/Paginator mismatch' unless
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page.paginator == self
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end
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page = page.to_i
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@current_page_number = has_page_number?(page) ? page : 1
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end
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# Returns a Page object representing this paginator's current page.
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def current_page
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@current_page ||= self[@current_page_number]
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end
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alias current :current_page
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# Returns a new Page representing the first page in this paginator.
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def first_page
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@first_page ||= self[1]
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end
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alias first :first_page
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# Returns a new Page representing the last page in this paginator.
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def last_page
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@last_page ||= self[page_count]
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end
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alias last :last_page
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# Returns the number of pages in this paginator.
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def page_count
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@page_count ||= @item_count.zero? ? 1 :
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(q,r=@item_count.divmod(@items_per_page); r==0? q : q+1)
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end
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alias length :page_count
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# Returns true if this paginator contains the page of index +number+.
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def has_page_number?(number)
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number >= 1 and number <= page_count
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end
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# Returns a new Page representing the page with the given index
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# +number+.
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def [](number)
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@pages[number] ||= Page.new(self, number)
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end
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# Successively yields all the paginator's pages to the given block.
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def each(&block)
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page_count.times do |n|
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yield self[n+1]
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end
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end
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# A class representing a single page in a paginator.
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class Page
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include Comparable
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# Creates a new Page for the given +paginator+ with the index
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# +number+. If +number+ is not in the range of valid page numbers or
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# is not a number at all, it defaults to 1.
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def initialize(paginator, number)
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@paginator = paginator
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@number = number.to_i
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@number = 1 unless @paginator.has_page_number? @number
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end
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attr_reader :paginator, :number
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alias to_i :number
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# Compares two Page objects and returns true when they represent the
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# same page (i.e., their paginators are the same and they have the
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# same page number).
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def ==(page)
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return false if page.nil?
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@paginator == page.paginator and
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@number == page.number
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end
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# Compares two Page objects and returns -1 if the left-hand page comes
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# before the right-hand page, 0 if the pages are equal, and 1 if the
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# left-hand page comes after the right-hand page. Raises ArgumentError
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# if the pages do not belong to the same Paginator object.
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def <=>(page)
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raise ArgumentError unless @paginator == page.paginator
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@number <=> page.number
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end
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# Returns the item offset for the first item in this page.
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def offset
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@paginator.items_per_page * (@number - 1)
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end
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# Returns the number of the first item displayed.
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def first_item
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offset + 1
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end
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# Returns the number of the last item displayed.
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def last_item
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[@paginator.items_per_page * @number, @paginator.item_count].min
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end
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# Returns true if this page is the first page in the paginator.
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def first?
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self == @paginator.first
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end
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# Returns true if this page is the last page in the paginator.
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def last?
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self == @paginator.last
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end
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# Returns a new Page object representing the page just before this
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# page, or nil if this is the first page.
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def previous
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if first? then nil else @paginator[@number - 1] end
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end
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# Returns a new Page object representing the page just after this
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# page, or nil if this is the last page.
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def next
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if last? then nil else @paginator[@number + 1] end
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end
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# Returns a new Window object for this page with the specified
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# +padding+.
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def window(padding=2)
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Window.new(self, padding)
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end
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# Returns the limit/offset array for this page.
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def to_sql
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[@paginator.items_per_page, offset]
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end
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def to_param #:nodoc:
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@number.to_s
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end
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end
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# A class for representing ranges around a given page.
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class Window
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# Creates a new Window object for the given +page+ with the specified
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# +padding+.
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def initialize(page, padding=2)
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@paginator = page.paginator
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@page = page
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self.padding = padding
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end
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attr_reader :paginator, :page
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# Sets the window's padding (the number of pages on either side of the
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# window page).
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def padding=(padding)
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@padding = padding < 0 ? 0 : padding
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# Find the beginning and end pages of the window
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@first = @paginator.has_page_number?(@page.number - @padding) ?
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@paginator[@page.number - @padding] : @paginator.first
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@last = @paginator.has_page_number?(@page.number + @padding) ?
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@paginator[@page.number + @padding] : @paginator.last
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end
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attr_reader :padding, :first, :last
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# Returns an array of Page objects in the current window.
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def pages
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(@first.number..@last.number).to_a.collect! {|n| @paginator[n]}
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end
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alias to_a :pages
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end
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end
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end
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end
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