How to paginate custom resources with kaminari helpers?

Question

I have some custom resources queried over a rest API. I would like to make use of kaminari's pagination view helpers (e.g. page links).

I understand kaminari can paginate array-like resources when they are all available, however, my resources are expensive to query and store all at once.

Answer 1

Found this article helpful but outdated: https://kirshatrov.com/2015/11/08/kaminari-custom-query/

Ended up writing my own adapter:

class KaminariAdapter
  def initialize(page)
    @page = page.to_i
    @limit = 1
  end

  def entries(page)
    raise "Must be implemented by subclass"
  end

  def total_count
    raise "Must be implemented by subclass"
  end

  def entry_name(*arg)
    @entry_name ||= 'entry'.freeze
  end

  def current_page
    @page
  end

  def total_pages
    @total_pages ||= (total_count.to_f / @limit).ceil
  end

  def limit_value
    @limit
  end

  def offset
    (@page - 1) * @limit
  end

  def offset_value
    offset
  end

  def all
    entries(@page)
  end

  def size
    all.count
  end
end

Children must implement entries(page) and total_count methods. Here's an example:

class CustomPagination < KaminariAdapter
  def initialize(*args)
    super
    @all_entries = [1, 2, 3, 4, 5, 6, 7]
    @limit = 2
  end

  def entries(page)
    @all_entries[offset..(offset + @limit - 1)]
  end

  def total_count
    @all_entries.count
  end
end

Can be used like this:

test_controller.rb

def index
  @entries = CustomPagination.new(params[:page].to_i)
end

test/index.html.erb

<% @entries.all.each do |entry| %>
  <%= entry %>
<% end %> 

<%= paginate @entries %>
<%= page_entries_info @entries %>