Integrating JSONAPI::Deserialization

require 'jsonapi/deserializable'

class ApplicationController < ActionController::API
  include JSONAPI::Deserialization

  before_action :deserialize_jsonapi_request

  private

  def deserialize_jsonapi_request
    return unless request.content_type == 'application/vnd.api+json'

    hash = request.request_parameters
    hash = hash.to_unsafe_hash if Rails::VERSION::MAJOR >= 5
    ActiveModelSerializers::Deserialization.jsonapi_parse!(hash)
  rescue ActiveModelSerializers::Deserialization::InvalidDocument => e
    render jsonapi_errors: e.errors, status: :unprocessable_entity
  end
end

1. We require the jsonapi/deserializable library to access the JSONAPI::Deserialization module.

2. Inside the ApplicationController, we include the JSONAPI::Deserialization module. This mixes in the deserialization functionality into the controller.

3. We define a before_action callback that calls the deserialize_jsonapi_request method before each action in the controller.

4. In the deserialize_jsonapi_request method:

   4.1 We check if the request's content_type is application/vnd.api+json. If

   not, we skip deserialization.

   4.2 We retrieve the request parameters using request.request_parameters.

   4.3 If using Rails 5 or later, we convert the parameters to an unsafe hash

   using to_unsafe_hash for compatibility.

   4.4 We call ActiveModelSerializers::Deserialization.jsonapi_parse! to parse

   and deserialize the JSONAPI request parameters.
   4.5 If an ActiveModelSerializers::Deserialization::InvalidDocument exception

   is raised during deserialization (indicating invalid JSONAPI input), we

   render a JSONAPI error response with a status of:unprocessable_entity.

5. With this setup, the JSONAPI::Deserialization module will be included in the ApplicationController, and the deserialize_jsonapi_request method will be called before each action to deserialize the incoming JSONAPI request parameters.

6. Remember to have the jsonapi-serializer gem (or a similar JSONAPI serialization/deserialization library) installed in your application for this code to work.