JSONAPI :: Create a Singleton Resource Profile

A singleton resource is a api url call that will always lead to only one resource. A real world use case would be "GET /profile" and "PATCH /profile" which (respectively) would get the profile record of the current user and update the record of the current record.

As mentioned in the README documentation in the routes section,, you need a singular resource route without an id:

config/routes.rb:

jsonapi_resource :profile

You need to record the current logged in user via a context method on one of your controllers or across all controllers using ApplicationController:

def context { user: current_user } 
end

and then you need to override the find_by_key method on the profile resource:

def self.find_by_key(key, options = {})
  context = options[:context]
  model = context[:user]
  fail JSONAPI::Exceptions::RecordNotFound.new(key) if model.nil?
  resource_for_model(model).new(model, context)
end

Note that your controller will also be in the singular profile_controller.rb not `profiles_controller.rb'

Then the singleton calls ( GET /profile, POST /profile, PUT /profile, DELETE /profile ) will work ( although the json api type will still be plural type: 'profiles', )

Note: singletons are not officially supported by the spec, so there may be clients that are not compatible with this approach.