gaorlov / json_api_model

Wrapper for JsonApiClient for in-app business logic.

JsonApiModel

Much like ActiveRecord is an ORM on top of your database, JSON API Client is an ORM specific to a service. This gem is the app/models/ on top of json_api_client.

Yes, you can put business in the client, but if you need to distrubute the gem, you will want that to live somewhere else. This gem provides a thin wrapper layer to let you do that.

Installation

Add this line to your application's Gemfile:

gem 'json_api_model'

And then execute:

$ bundle

Or install it yourself as:

$ gem install json_api_model

Usage

Using the model wrappers is pretty straighforward. It thinly wraps JsonApiClient to separate communication defintions from your in-app business specific logic. To specify what client class your model is wrapping, use the wraps method.

Any instance or class(non-query) level method will fall thorugh to the client.

Associations

You can define simple associations that behave very much like ActiveRecord associations. Once you define your association, you will have a method with that name that will do the lookups and cache the results for you.

• belongs_to association: the base object has to have the association id
  • will return a single object or nil
• has_one: the assiociation object has the id of the base.
  • will return a single object or nil
• has_many: the association object has the id of the base.
  • will return an array

Assocaition Options

Associations have some of the standard ActiveRecord options. Namely:

• class: specifies the class to find the record in.

    has_one :special_thing, class: Thing

• class_name: specifies the class w.o having to have the class defined. Handy for circular dependencies

    class Person < JsonApiModel::Model
      wraps MyApi::Client::Person
      has_one :nickname, class_name: "Pesudonym"
    end
  
    class Pseudonym < JsonApiModel::Model
      wraps MyApi::Client::Pseudonym
      belongs_to :bearer, class_name: "Person"
    end

NOTE: Due to perf implications the following are only available for local classes (not things that come through the relatinships block in the payload). This will never ever be available for remote models.

• through: many to may association helper.

  class Person < JsonApiModel::Model
    wraps MyApi::Client::Person
    has_many :person_foods
    has_many :favorite_foods, through: :person_foods, class_name: "Food"
  end

  # locally stored models that respond to #{model_class}_id
  class PersonFood < ActiveRecord::Base
    belongs_to :person
    belongs_to :food
  end

  class Food < ActiveRecord::Base
  end

• as: specifies what the associated object calls the caller

    class Person < JsonApiModel::Model
    wraps MyApi::Client::Person
      has_many :images, as: :target
    end
  
    class Image < ActiveRecord::Base
      belongs_to :target
    end

NOTE: only works for has_one and has_many

Example

If you have an app that talks to a user service. Here's how your User model might look:

module UserService
  class User < JsonApiModel::Model
    wraps UserService::Client::User

    def lucky_number
      42
    end
  end
end

And the interaction with it is identical as how you would work with the client:

# fetching looks identical to as json_api_client (because it thinly wraps it)
user = UserService::User.where( id: 8 ).first

# now you can access your app logic
user.lucky_number

# => 42

# but also transparently access the client properties
user.id
# => 8

# creating new users
new_user = UserService::User.new name: "greg"
# => #<UserService::User:0x000055e1fc1c8c00 @client=#<UserService::Client::User:@attributes={"type"=>"users", "name"=>"greg"}>>
new_user.save
# => true

# and now that the record is saved, you can search for it and get back a JsonApiModel back to keep working with
UserService::User.where( name: "greg" ).first
# => #<UserService::User:0x000055e1fc1c8c00 @client=#<UserService::Client::User:@attributes={"type"=>"users", "name"=>"greg", "id"=>"9"}>>

Rendering

If you need to propagate your response set up, JsonApiModel adds as_json handling so that:

class WhateversController < ApplicationController
  def index
    render json: MyService::MyModel.where( params ).all
  end
end

Would produce the standard JSONAPI response of:

{
  data: data,
  meta: meta
}

But if that's not the structure you want, you can modify the to_json output as:

class MyModelInRussianConroller < ApplicationController

  def индекс
    @response = MyModel.where( params ).all

    @response.as_json do |data, meta|
      {
        данные: data,
        мета: {
          счёт: meta["record_count"],
          страницы: meta["page_count"]
        }
      }
    end
  end
end

Preloading

If you have a model that you need to bulk load along with its associations, in ActiveRecord, you can do MyModel.where( args ).preload( :association, other_association: :nested association ). Well, you can do that here as well.

NOTE(1): consider the complexity, especially for remote models

NOTE(2): for remote models, the preloader does not currently autopage

Example

Let's say you have a mixed environemnt of local and remote models, like so:

module Example
  class User < JsonApiModel::Model
    wraps Example::Client::User

    # remote model
    belongs_to :org, class_name: "Example::Org"

    # local model
    has_one :profile
  end

  class Org < JsonApiModel::Model
    wraps Example::Client::Org
  end
end

class Profile < ActiveRecord::Base
  belongs_to :user
end

You can bulk prefetch associations for a block of Users

Example::User.where( name: [ "Greg", "Mike" ] ).preload( :org, :profile )

Will make 3 calls:

• User to fetch .where( name: [ "Greg", "Mike" ])
• Org to fetch the orgs associated with those users, as returned in their relationship blocks
• Profile to fetch where( user_id: users.map( &:id ) )

Or if you already have your users loaded, you can call

JsonApiModel::Associations::Preloader.preload( users, :org, :profile )

and that'll do the same thing, minus the User call

Configuration

If you don't want to override the connection configuration of the client gem in an initializer, you can modify the connection options inside an inhrited class.

module MyService
  class Base < JsonApiModel::Model

    wraps MyService::Client::Base

    # delegates connection options to the Client::Base without having to modify the gem
    self.connection do | conn |
      conn.use Faraday::Response::Logger, Rails.logger

      conn.faraday.options.merge!(
        open_timeout: 5,
        timeout: 5
      )
    end
  end
end

Monitoring

JsonApiModel emits several ActiveSupport::Notifications events you can subscribe to:

• find.json_api_model: fires on every find/all/to_a call. Probably most common.

  key	value
  url	full url hit
  args	args passed into the requestor

• first.json_api_model: fires on Model.first

  key	value
  url	full url hit

• last.json_api_model: fired on Model.last

  key	value
  url	full url hit

NOTE: By default the instrumenter is null, so be sure to configure your app to actually have a notifier and subscribe to the events

# config/initializers/json_api_model.rb
JsonApiModel.instrumenter = ActiveSupport::Notifications.instrumenter

ActiveSupport::Notifications.subscribe "find.json_api_model" do |name, started, finished, unique_id, payload|
  Rails.logger.debug ['notification:', name, started, finished, unique_id, payload].join(' ')
end

Known Issues

• Due to an open issue in JsonApiClient scopes are modifiable, which means that scope.where( params ) now permanently has those params in it.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/gaorlov/json_api_model. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the JsonApiModel project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.