Clean Pagination

The simplest, most flexible, most standards-compliant pagination gem there is. Pairs nicely with begriffs/angular-paginate-anything.

Usage

class ApplicationController < ActionController::Base
  include CleanPagination

  # Using activemodel
  def index
    max_per_page = 100

    paginate Bla.count, max_per_page do |limit, offset|
      render json: Bla.limit(limit).offset(offset)
    end
  end

  # Using some custom data
  def numbers
    paginate Float::INFINITY, 100 do |limit, offset|
      render json: (offset...offset+limit).to_a
    end
  end
  
  # Using optional settings
  def options
    begin
      paginate Foo.scope.count, max_per_page, allow_render: false, raise_errors: true do |limit, offset|
        respond_with Foo.scope.limit(limit).offset(offset)
      end
    rescue RangeError
      render json: { error: { message: "invalid pagination range" } }
    end
  end
end

Benefits

• HTTP Content-Type agnoticism. Information about total items, selected ranges, and next- previous-links are sent through headers. It works without modifying your API payload in any way.
• Graceful degredation. Both client and server specify the maximum page size they accept and communication gracefully degrades to accomodate the lesser.
• Expressive retrieval. This approach, unlike the use of per_page and page parameters, allows the client to request any (possibly unbounded) interval of items.
• Semantic HTTP. Built in strict conformance to RFCs 2616 and 5988.

Under the hood

To prevent this gem from rendering while still allowing it to set headers and response codes, pass allow_render: false to paginate. This may be used to avoid DoubleRenderError situations.

To handle the invalid request range condition in your app, pass the raise_errors: true option. This will raise a RangeError which you can rescue (and thus control what is rendered). Headers will still be set.

[TODO: explain what the headers mean.] Until this is written you can consult the tests for an idea how it works, or use a client that is compatible, such as begriffs/angular-paginate-anything.