Shale

Paginator for Amber Framework

Installation

Add this to your application's shard.yml:

dependencies:
  shale:
    github: c910335/shale

Usage

Note: Shale only supports Granite and PostgreSQL currently.

# config/initializers/paginator.cr
require "shale/amber" # for page helper
require "shale/granite" # for granite adapter
Shale.base_url = "https://base.url"

# src/controllers/application_controller.cr
class ApplicationController < Amber::Controller::Base
  include Shale::Amber::PageHelper(Shale::Granite::Adapter)
end

# src/controller/sample_controller
class SampleController < ApplicationController
  def index
    samples = paginate Sample
    # render your view with samples
  end
end

Shale::Amber::PageHelper#paginate reads parameters from params and path from request.path and adds links to response.headers, then returns the paginated data.

Parameters

Response Header

reference: RFC 5988 - Web Linking

Link: <https://base.url/samples?page=2&per_page=3&sort=id&direction=desc>; rel="prev",
  <https://base.url/samples?page=4&per_page=3&sort=id&direction=desc>; rel="next",
  <https://base.url/samples?page=1&per_page=3&sort=id&direction=desc>; rel="first",
  <https://base.url/samples?page=8&per_page=3&sort=id&direction=desc>; rel="last"

Default Values

# Global
Shale.base_url = "https://base.url" # required
Shale.path = "/path"
Shale.page = 1
Shale.per = 8
Shale.order = :id
Shale.direction = :desc

# Scoped
class SomeController
  include Shale::Amber::PageHelper(Shale::Granite::Adapter)

  shale_base_url = "https://base.url"
  shale_path = "/path"
  shale_page = 1
  shale_per = 8
  shale_order = :id
  shale_direction = :desc
end

Customization

Paginator

This is what Shale::Amber::PageHelper looks like.

require "shale"

module Shale::Amber::PageHelper(Adapter)
  include Shale::Paginator(Adapter)

  def paginate(model)
    paginate model do |p|
      p.path request.path
      p.page params["page"].to_i if params["page"]?
      p.per params["per_page"].to_i if params["per_page"]?
      p.order params["sort"] if params["sort"]?
      p.direction params["direction"] if params["direction"]?
      p.headers response.headers
    end
  end
end

You can change the source of path or parameters by building your own paginator.

Adapter

• inherits Shale::BaseAdapter
• implements #count(model) and #select(model) with #page, #per, #order and #direction

For example, this is an ArrayAdapter.

require "shale"

class ArrayAdapter < Shale::BaseAdapter
  def count(array)
    array.size
  end

  def select(array)
    sorted = if direction.to_s == "desc"
               array.sort { |a, b| b[order] <=> a[order] }
             else
               array.sort { |a, b| a[order] <=> b[order] }
             end
    sorted[(page - 1) * per, per]
  end
end

Which is useful to paginate Array(Hash(Symbol, Int32)).

class ArrayPaginator
  include Shale::Paginator(ArrayAdapter)
end

array = Array.new(10) do |i|
  {:number => 10 - i}
end

paginated = ArrayPaginator.new.paginate array do |p|
  p.page 2
  p.per 3
  p.order :number
  p.direction :asc
end

pp paginated # => [{:number => 4}, {:number => 5}, {:number => 6}]

Development

Since Shale depends on PostgreSQL, we run specs with Docker.

$ docker-compose build
$ docker-compose run migrate
$ docker-compose run spec

Contributing

1. Fork it (https://github.com/c910335/shale/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• c910335 Tatsiujin Chin - creator, maintainer