Active Admin Resource

Extension of ActiveResource to allow integration with ActiveAdmin.

Disclaimer

This gem is work in progress. There is only partial support of ActiveAdmin for now, and the are some specific limitation and requirements that need to be considered when using it.

Pull Requests with improvements are welcomed :)

Installation

Add this line to your Rails application's Gemfile:

gem 'active_admin_resource', github: "budacom/activeadmin_resource"

And then execute:

$ bundle

Usage

This gem provides a base class that extends from ActiveResource and patches some missing functions in both ActiveAdmin and ActiveResource. The patches are executed when the gem is loaded.

ActiveAdminResource::Base

This is the base class that you need to use to create ActiveAdmin enabled ActiveResource models. You need to extend your model with this base class, and define the minimum fields required by ActiveResource as in the following example:

class Market < ActiveAdminResource::Base
  self.site = "http://localhost/api/"

  schema do
    attribute 'id', :string
    attribute 'name', :string
    attribute 'base_currency', :string
    attribute 'quote_currency', :string
  end
end

This base class allows also to perform signed requests using the Authograph gem. To enable this, the class must implement the class method self.secret and return the private key in that method. Additionaly, an id of the requester can be provided by implementing the self.agent_id method as the following example shows:

class Account < ActiveAdminResource::Base
  self.site = "http://localhost/signed_api/"

  def self.agent_id
    #Return id
  end

  def self.secret
    #Return secret
  end

  schema do
    attribute 'id', :integer
    attribute 'name', :string
  end
end

ActiveResource has partial support for relations between models. You can specify has_one and has_manyrelations just like its is done in ActiveRecord:

class Account < ActiveAdminResource::Base
  self.site = "http://localhost/signed_api/"

  has_one :agent_data
  has_many :withdrawals

  def self.agent_id
    #Return id
  end

  def self.secret
    #Return secret
  end

  schema do
    attribute 'id', :integer
    attribute 'name', :string
  end
end

The difference in how relations are handled is that for the subelement of a model (in this example AgentData) the url must include the parent url with a symbol indicating the id of the parent record (in this example :account_id).

class AgentData < ActiveAdminResource::AgentDataBase
  self.site = "http://localhost/signed_api/accounts/:account_id"

  def self.agent_id
    #Return id
  end

  def self.secret
    #Return secret
  end

  schema do
    attribute 'a', :string
  end
end

When accessing the subelement and trying to perform an action, this extra symbol must be included as a parameter to complete the url:

Account.find(4).agent_data.update_attributes(a: "asdf", account_id: 4)

ActiveAdminResource::AgentDataBase

An additional base class called AgentDataBase is provided to model the special case of an AgentData object:

class AgentData < ActiveAdminResource::AgentDataBase
  self.site = "http://localhost/signed_api/"

  def self.agent_id
    #Return id
  end

  def self.secret
    #Return secret
  end

  schema do
    attribute 'a', :string
  end
end

When registering an ActiveAdminResource model with ActiveAdmin some additional considerations must be taken:

• Batch actions are not supported, so they should be disabled.
• The find_collection method of controller must be overriden and return a paginated array as a result.
• Pagination is supported by providing pagination info in the server response. The currently supported pagination format expect a meta field in the response with a dictionary that has the following fields describing the pagination: total_pages, total_count and current_page. When a response is requested, the pagination info is stored in Model.format.pagination_info and can be used to paginate the info accordingly.

The following example shows an ActiveAdminResource model being registered for ActiveAdmin and using the pagination schema explained before.

  
ActiveAdmin.register Account do
  config.batch_actions = false

  filter :names, as: :string, label: "Names"
  filter :surnames, as: :string, label: "Surnames"

  controller do
    def find_collection
      default_per_page = 20
      per_page = params.fetch(:per_page, default_per_page)
      query_params = params.fetch(:q, nil)
      search_params = query_params.nil? ? {} : query_params.permit!.to_h
      @search = OpenStruct.new(search_params.merge(conditions: []))
      result = Account.find(:all, params: {
        order: params.fetch(:order, nil),
        page: params.fetch(:page, 1),
        per: per_page,
        search: search_params
      })
      pagination_info = Account.format.pagination_info
      offset = (pagination_info["current_page"] - 1) * per_page
      Kaminari.paginate_array(result, limit: result.count, offset: offset, total_count: pagination_info["total_count"])
    end
  end
end

Limitations and Poorly tested cases

As explained before, there are several limitations and poorly tested cases in the current version:

• Batch actions are not supported
• POST, PUT and DELETE actions are not tested well and may have issues